Igor Make a new wave

Question

I have 2 waves of data. Z_EC is proton number, N_EC is neutron number, and EC_pure is a flagged wave based on certain perimeters, IE flag "1" if meets criteria, "0" if not.

I'm trying make a new proton and neutron wave that will have the correct values based on whether or not EC_pure is a 1 or 0 (If 1 match P to N; if 0 do nothing). However, every time I run my function, the new waves fill in the P and N values even when EC_pure = 0

Function plotECzn()
    wave EC_pure, Z_EC, N_EC
    variable i, j
    variable len = numpnts(Z_EC)
    Duplicate/O Z_EC Z_pure
    Duplicate/O Z_EC N_pure
    For(i=0; i<len; i+=1)
     For(j=0; j<121; j+=1)
        If(EC_pure[j] == 1)
        Z_pure[i] = Z_EC[i]
        N_pure[i] = N_EC[i]
        
    Endif
 Endfor
Endfor 
End

Answer 1

A more compact way to write this is:

Function ListECzn()
    WAVE EC_pure, Z_EC, N_EC
    variable Len = NumPnts(EC_pure)
    Make/O/D/N=(Len) Z_pure, N_pure
    Z_pure[] = (EC_pure[p] == 1) ? Z_EC[p] : NaN
    N_pure[] = (EC_pure[p] == 1) ? N_EC[p] : NaN
    WaveTransform zapnans Z_pure
    WaveTransform zapnans N_pure
End

These conditional assignments are really useful. The syntax of Z_pure[] = (EC_pure[p] == 1)? Z_EC[p]: NaN Z_pure[] = (EC_pure[p] == 1)? Z_EC[p]: NaN means: assign the following to each row of Z_pure - if EC_Pure is 1 then assign the Z_EC value, if not, assign NaN. Then you just delete the NaNs. Done.

Another possibility would be to duplicate the waves and assign NaNs if EC_Pure == 0 and then zapnans.

Answer 2

Function ListECzn()
    WAVE EC_pure, Z_EC, N_EC
    wavestats/Q EC_pure
    variable N_Candidates = V_Sum
    Make/O/D/N=(N_Candidates) Z_pure, N_pure    
    variable Len = NumPnts(EC_pure)
    variable i
    variable j = 0
    For(i=0; i<Len; i+=1)
        If(EC_pure[i] == 1)
            Z_pure[j] = Z_EC[i]
            N_pure[j] = N_EC[i]
            j += 1
        EndIf
    EndFor
End