How to normalise two waves in a quicker way
Igor_user
I have two sets of data. Each has two waves. The first one has X1, Y1 and the second has X2, Y2.
I'd like to normalise both Y1 and Y2 so that both will have the maximum point equal to 1, and other Y points will be scaled to the correct ratio accordingly.
I used to do this by just finding the maximun point and dividing the whole wave by its maximum to get a new wave. But if the wave has thousands of points, it here a quicker way of doing it?
cheers,
Wavemax(wave) returns the maximum value of the 'wave
Duplicate wave0, wave_nor
wave_nor=wave0/wavemax(wave0)
I usually use like this.
October 21, 2014 at 02:02 am - Permalink
this will be fairly slow because WaveMax is evaluated for every point within the implicit loop for wave arithmetic. Better use something like:
wave w
variable ref = StartMStimer
Duplicate/O w w_norm
variable mx = wavemax(w)
Multithread w_norm /= mx
variable tme = stopMStimer(ref)
printf "%g seconds \r", tme/1e6
end
If the thread opener tried this already, then I don't know a faster method!
October 21, 2014 at 05:39 am - Permalink
MatrixOP/O Y1norm = Y1/maxval(Y1)MatrixOP has been highly optimized for speed. If you can do it with MatrixOP, it will almost always be faster, though with anything like this actual measurements are required to be sure of that.
And in Igor 7 where possible it will take advantage of multiple processors for even greater speed. Igor 7 is not yet in beta testing, though.
John Weeks
WaveMetrics, Inc.
support@wavemetrics.com
October 21, 2014 at 09:28 am - Permalink
Hello,
I was wondering how I can add a specific range in the X axis to calculate the maxval, for example from 0.2 to 0.5 seconds. I have done this with wavemax(Wave1, 0.2, 0.5) but doesn't work with matrixOP
May 2, 2018 at 11:49 am - Permalink
setscale/I x 0,1,junk // Set the X scaling
Variable maxv = wavemax(junk, 0.2, 0.5) // find the maximum value within the specified X range
matrixOP junknorm = junk/maxv
--- or ---
junk /= maxv
MatrixOP here is convenient if you want the result in a second wave, because it automatically makes the wave "junknorm" for you. The simple wave assignment is easy to write if you want to overwrite your original data (which is usually not a good idea, but may be appropriate if it is some sort of intermediate result).
John Weeks
WaveMetrics, Inc.
support@wavemetrics.com
May 2, 2018 at 12:59 pm - Permalink
Matrixop/o temp = subrange(wv,p0,p1,0,0) //temp now holds the data in subrange x0-x1
//now you can run matrix op commands in this (in fact, you could also nest this in the matrixop command you quoted)
matrixop/o result = temp/maxval(temp)
//then, finally, you would probably want to copy the x scaling from the original wave
setscale/p x,dimoffset(wv,0)+x0,dimdelta(wv,0),waveunits(wv,0),result
subrange works for rows and columns, there are other commands available to work with higher dimensions in matrixop.
May 2, 2018 at 01:10 pm - Permalink