RandomLocation.hoc

fprint("RandomLocation_ver = '$Revision: 1.2 $';\n")

/*
RandomLocation

rl = new RandomLocation(SectionList)
rl.loc(PointProcess)

relocates the PointProcess to a random location with respect to
uniform distribution based on position.
SectionList defines the set of sections to sample.
PointProcess must have a loc() member function.
There must be a default section declared to measure distance from.
*/

begintemplate RandomLocation

public loc
public total_length, dstart, dend
objectvar seclist, ran 	

proc init() { local 
    dstart = -1
    if ( numarg () == 4) {
        dstart = $3
        dend = $4
    }
    seclist = $o1
    ran = new Random($2)
    total_length = 0
    forsec seclist { 
        // Add length of current section 
        total_length = total_length + L 

        // Find the distance of the ends from the origin
        d0 = distance(0)
        d1 = distance(1)
        
        // This should remove any length of section beyond the 
        // Limits specified by dstart and dend
        if ( min(d0,d1) < dstart ) {
            total_length = total_length - (dstart-min(d0,d1))
        }
        if ( max(d0,d1) > dend ) {
            total_length = total_length - (max(d0,d1)-dend)
        }
    }
}

// randomize location of synapse
func loc() {local l, done, rpos, secx, dx, gl, lsec, d0, d1
    rpos = ran.uniform(0, total_length)
    done = 0
    l = 0                       // Cumulative length
    //  distance()  // assumes soma is currently accessed         
    // sets the currently-accessed section as the origin
    forsec seclist {
        lsec = L
        d0 = distance(0)
        d1 = distance(1)
        
        // This should remove any length of section beyond the 
        // Limits specified by dstart and dend
        if ( min(d0,d1) < dstart ) {
            lsec = lsec - (dstart-min(d0,d1))
        }
        if ( max(d0,d1) > dend ) {
            lsec = lsec - (max(d0,d1)-dend)
        }
        l = l + lsec               // L is length of section
        if (l > rpos) {
            //      print l, " ", rpos, " ", L
            secx = (rpos - l + L)/L
            //      print secx
			      $o1.loc(secx)
            dx = distance(secx) 
            print secname(), " ", secx, " ", dx
            rpos = 1e20   // a break would screw up the stack?
        }
    }
    return secx
}

endtemplate RandomLocation