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Interpolation of step-like function

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muh

France
14 Posts

Posted - 01/06/2016 : 12:31:37 PM

Hello. I am trying to interpolate a step-like function. It stays constant for some range of X, then jumps to a new value, stays constant etc. Usual procedure seem to work very poorly. Here is example. Is there a workaround?

X Y Interpolated value just to the left of a point
F= col(y)(col(x)-0.001)
0.000000 10.67 -0.69
0.519985 10.67 10.67
0.519985 2.05 10.67
0.530043 2.05 10.67
0.530043 -2.32 10.67
0.531418 -2.32 10.67
0.531418 -3.37 10.67
0.669557 -3.37 10.67
0.669557 78.66 10.67
0.694520 78.66 10.67
0.694520 -27.05 10.67
0.718891 -27.05 10.67
0.718891 0 10.67
1.609484 0 10.67
1.609484 -0.53 10.67
8.549832 -0.53 10.67
8.549832 -0.96 10.67
8.552062 -0.96 10.67
8.552062 -0.76 10.67
8.552408 -0.76 10.67
8.552408 -0.69 10.67
-- -0.69 --

Hideo Fujii

USA
1582 Posts

Posted - 01/06/2016 : 4:21:24 PM

Hi muh,
Not sure if I understand correctly, but it seems you simply need to locate the position of the given
X value on the X axis, then read out the Y level. Can you try the following method:

Here, I inserted a dummy Y column(col(D1)) filled with row numbers, apply the "Interpolate/Extrapolate
Y from X"(interp1) for the specific X positions (col(D)), get the location's row# (col(F)), and finally
read out the Y value at the location (col(G)).

You can script for these steps easily. Hope this helps.

--Hideo Fujii
OriginLab

Edited by - Hideo Fujii on 01/06/2016 5:50:59 PM

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