synchronize time base for multiple waves

//___________________________________________________________________________________________________   
// average a wave which may be on an uneven timebase
Function/WAVE AvgDateTime(Wave dataWv, Wave timeWv, double secs)
 
    [double beginPnt, double endPnt] = WaveMinAndMax(timeWv)
    int n = round((endPnt - beginPnt) / secs),i,j,k
    
    Make /O /N=(n) /FREE outWv = NaN
    
    do
        FindValue /Z /S=(i) /V=(beginPnt + (i+1 * secs)) /T=(secs / 2) timeWV
        
        k = V_value
        
        WaveStats /Q /M=1 /R=[j,k] dataWv
        
        outWv[i] = V_avg
        
        j = V_value
        
        i++
    while (i < n)   
    
    return outWv
End

//___________________________________________________________________________________________________   
// get the limits of waves passed as a list
Function [double minVar,double maxVar] findLimits(String wavList)
 
    int num = ItemsInList(wavList),i
    Make /O /D /FREE /N=(2 * num) limits
    
    for (i = 0;i<num;i++)
        Wave wav = $StringFromList(i,wavList)
        
        WaveStats /Q /M=1 wav // there may be NaN values
        
        limits[2*i,2*i+1] = {V_min,V_max}
    endfor
    
    [minVar,maxVar] = WaveMinandMax(limits) // get the limits
    
    return [minVar,maxVar]
End

// get the extent of the time variables - you could manually set your own limits
[double minVar, doublemaxVar] = findLimits("insrument_1_time;instrument_2_time;")
 
// make a regular time wave
Make /D /N=(1 + maxVar - minVar) timewave = x+minVar 

//___________________________________________________________________________________________________
// Performs an expansion but doesn't round t1 and t2 to even fractional seconds. Finds nearest time in t2 within the supplied delta.
// Especially useful for data at faster than 1Hz that isn't on an even time base.
// 20200303 added ability to expand 2D waves, assumes dim0 is the one being expanded 
Function/WAVE expand2nearest(t1, w1, t2, delta)
    wave t1, w1, t2
    variable delta
    
    variable x1, x2, n1, n2 , diff1, diff2
    n1 = numpnts(t1)    //length of timewave1
    n2 = numpnts(t2)    //length of timewave2
    
    Make /N=(n2,DimSize(w1,1)) /FREE w2=NaN 
    
    do
        diff1 = abs(t2[x2] - t1[x1])
        if (x1+1<n1)
            diff2 = abs(t2[x2] - t1[x1+1])  // only test this if not on last row of t1, else it will be index out of range error.
        else    
            diff2=diff1
        endif
        if ((diff1 <=  diff2) * (diff1 <= delta) * (numtype(w1[x1]) == 0))    //if this difference is smaller than the next difference, and difference is less than delta, and isn't NaN.
            w2[x2][]=w1[x1][q]
            x1+=1
            if (x1 == n1)   // That was the last point for w1, so break. We're done.
                break
            endif
            
            if (x1+1 < n1)
                if ((abs(t1[x1] - t2[x2])) < (abs(t1[x1+1] - t2[x2])))  //only increment x2 if the NEXT point in t1 is farther from t2 than the current point in t1
                    x2+=1
                endif
            else        // can't test if next row would be closer because this is last row of w1. Just test if within delta.
                if (abs(t1[x1] - t2[x2]) > delta)
                    x2+=1
                endif
            endif
        else
            if ( t2[x2] < t1[x1] )
                x2+=1
            else
                x1+=1
            endif
        endif
    while((x2 < n2 )&&(x1< n1))
    
    return w2
end