# shift array to flat

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Munsell Randall on 7 Oct 2017
Edited: Cedric Wannaz on 7 Oct 2017
hello,
i have a 142 element array that generates a curve (attached). when a line is drawn from end to end the line is at a certain (unknown) slope. how could i adjust the values in the array so that when plotted and a line drawn from end to end of the curve, the slope is 0?
picture and array is attached.

Cedric Wannaz on 7 Oct 2017
Edited: Cedric Wannaz on 7 Oct 2017
plot( unnamed, 'b' ) ;
hold on ; grid on ;
x = (1 : length(unnamed)).' - 1 ;
slope = (unnamed(end) - unnamed(1)) / (length(unnamed) - 1) ;
y = unnamed - (unnamed(1) + x * slope) ;
plot( y, 'g' ) ;
but we often need something else :
plot( detrend( unnamed ), 'r' ) ;
with
>> mean( detrend( unnamed ))
ans =
-3.9612e-18
>> mean( y )
ans =
-0.0011
##### 2 CommentsShowHide 1 older comment
Cedric Wannaz on 7 Oct 2017
Edited: Cedric Wannaz on 7 Oct 2017
doc detrend : removes linear trend.
What I understood from your question was that you wanted the green line on my plot, which is the curve shifted up based on the value defined by the black line. If it is correct, this is what I compute/define as y.
Thinking a bit more about it, you may want
y = unnamed - x * slope ;
if you want the first value to match.