Index out of range for customized indices

Function/D findMode(w)
    wave w
       
        variable ic
    variable yvar
   
    variable minVolt = -0.070//mV
    variable maxVolt = -0.010//mV
    variable increment = .00025//mV
    variable mostCommonY = minVolt //WILL BE USED AS THE STARTING POINT FOR FINDING THE MAX, SEEN IN THIRD FOR LOOP
   
    Make/D/O/N = ((maxVolt - minVolt) / increment) yvarCandidates
    //sets the range of indices for above wave
    SetScale/I y, minVolt, maxVolt, "mV", yVarCandidates//THIS IS THE PART THAT MAY BE GIVING ME PROBLEMS
   
        //IF A GIVEN INDEX IS CROSSED BY VOLTAGE TRACE, A "TALLY" IS ADDED TO IT.
    for(yvar = minVolt; yvar < maxVolt; yvar += increment)//goes from -70mv to -10 mv just to be safe
        for(ic = x2pnt(w, 3); ic < x2pnt(w, 3.5); ic += 1) //3 and 3.5 is the X value and not the pnt (index, rather),
                                            // it is not always a round integer; its in seconds
            if((w[ic - 1] < yvar && w[ic] > yvar) || (w[ic - 1] > yvar && w[ic] < yvar))//if it crosses the thing
                yvarCandidates[yvar] += 1
            endif
        endfor
    endfor

    //GO THROUGH THE WAVE AND FIND THE MAX, RETURN ITS INDEX, WHICH ACTUALLY CORRESPONDS TO THE MODE VOLTAGE .
    variable i
    for(i = minVolt; i < maxVolt; i += increment)//goes from -70mv to -10 mv just to be safe
        if(yVarCandidates[i] > yVarCandidates[mostCommonY])//if it crosses the thing
            mostCommonY = i//equals idnex, which sould also be the index
        endif
    endfor//DEBUGGER POINTS HERE, BUT OF COURSE IT IS REALLY ERRORING OUT INSIDE LOOP
   

    KillWaves /Z yvarCandidates//save memory
    //RETURN A DOUBLE REPRESENTING THE MOST COMMON VOLTAGE
        return mostCommonY
end