diff --git a/docs/source/development/api_coverage.rst b/docs/source/development/api_coverage.rst
new file mode 100644
index 0000000000..eef44ba15b
--- /dev/null
+++ b/docs/source/development/api_coverage.rst
@@ -0,0 +1,187 @@
+.. _api_coverage:
+
+.. _pandas_api_coverage:
+
+Pandas API Coverage
+===================
+
+.. currentmodule:: mars.dataframe
+
+Input/output
+------------
+
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| Pandas API                                    | Mars DataFrame API                            | Description                                                           |
++===============================================+===============================================+=======================================================================+
+| :func:`pandas.read_pickle`                    |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.Dataframe.to_pickle`            |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.read_table`                     |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.read_csv`                       | :func:`read_csv`                              |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.DataFrame.to_csv`               | :func:`DataFrame.to_csv`                      |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.read_fwf`                       |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.read_clipboard`                 |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.DataFrame.to_clipboard`         |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.read_excel`                     |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.DataFrame.to_excel`             |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.read_json`                      |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.DataFrame.to_json`              |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.read_html`                      |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.DataFrame.to_html`              |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.read_xml`                       |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.DataFrame.to_xml`               |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.DataFrame.to_latex`             |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.read_feather`                   |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.DataFrame.to_feather`           |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.read_parquet`                   | :func:`read_parquet`                          |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.DataFrame.to_parquet`           | :func:`DataFrame.to_parquet`                  |  `to_parquet` writes data into directory instead of a single file     |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.read_orc`                       |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.read_sas`                       |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.read_spss`                      |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.read_sql_table`                 | :func:`read_sql_table`                        |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.read_sql_query`                 | :func:`read_sql_query`                        |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.read_sql`                       | :func:`read_sql`                              |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.DataFrame.to_sql`               | :func:`DataFrame.to_sql`                      |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.read_gbq`                       |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.read_stata`                     |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+
+General functions
+-----------------
+
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| Pandas API                                    | Mars DataFrame API                            | Description                                                           |
++===============================================+===============================================+=======================================================================+
+| :func:`pandas.melt`                           | :func:`melt`                                  |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.pivot`                          |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.pivot_table`                    |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.crosstab`                       |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.cut`                            | :func:`cut`                                   |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.qcut`                           | :func:`qcut`                                  |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.merge`                          | :func:`merge`                                 |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.merge_ordered`                  |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.merge_asof`                     |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.concat`                         | :func:`concat`                                |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.get_dummies`                    | :func:`get_dummies`                           |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.factorize`                      |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.unique`                         | :func:`unique`                                |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.wide_to_long`                   |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.isna`                           | :func:`isna`                                  |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.isnull`                         | :func:`isnull`                                |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.notna`                          | :func:`notna`                                 |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.notnull`                        | :func:`notnull`                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.to_numeric`                     | :func:`to_numeric`                            |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.to_datetime`                    | :func:`to_datetime`                           |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.to_timedelta`                   |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.date_range`                     | :func:`date_range`                            |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.bdate_range`                    |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.period_range`                   |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.timedelta_range`                |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.infer_freq`                     |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.interval_range`                 |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.eval`                           | :func:`eval`                                  |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+
+Series
+------
+
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| Pandas API                                    | Mars DataFrame API                            | Description                                                           |
++===============================================+===============================================+=======================================================================+
+| :func:`pandas.Series.astype`                  | :func:`Series.astype`                         |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.Series.convert_dtypes`          |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.Series.infer_objects`           |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.Series.copy`                    | :func:`Series.copy`                           |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.Series.bool`                    |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.Series.to_numpy`                |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.Series.to_period`               |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.Series.to_timestamp`            |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.Series.to_list`                 |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.Series.__array__`               |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.Series.get`                     |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.Series.at`                      | :func:`Series.at`                             |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.Series.iat`                     | :func:`Series.iat`                            |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.Series.loc`                     | :func:`Series.loc`                            |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.Series.iloc`                    | :func:`Series.iloc`                           |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.Series.__iter__`                |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.Series.items`                   |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.Series.iteritems`               |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.Series.keys`                    |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.Series.pop`                     |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
+| :func:`pandas.Series.xs`                      |                                               |                                                                       |
++-----------------------------------------------+-----------------------------------------------+-----------------------------------------------------------------------+
diff --git a/docs/source/development/index.rst b/docs/source/development/index.rst
index abc6271417..bf86f1e85a 100644
--- a/docs/source/development/index.rst
+++ b/docs/source/development/index.rst
@@ -10,3 +10,4 @@ Development
    operand
    oscar/index
    services/index
+   api_coverage
diff --git a/docs/source/reference/dataframe/general_functions.rst b/docs/source/reference/dataframe/general_functions.rst
index 5d4eb46510..1efd5c5e7a 100644
--- a/docs/source/reference/dataframe/general_functions.rst
+++ b/docs/source/reference/dataframe/general_functions.rst
@@ -16,6 +16,7 @@ Data manipulations
    melt
    merge
    qcut
+   unique
 
 Top-level missing data
 ~~~~~~~~~~~~~~~~~~~~~~
@@ -27,8 +28,16 @@ Top-level missing data
    notna
    notnull
 
-Top-level dealing with datetimelike
+Top-level dealing with numeric data
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. autosummary::
+   :toctree: generated/
+
+   to_numeric
+
+Top-level dealing with datetimelike data
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 .. autosummary::
    :toctree: generated/