# How to shift data sets automatically

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Damaris Litton el 23 de Mzo. de 2023
Respondida: Mathieu NOE el 27 de Mzo. de 2023
I have two sets of data that produce curves (see attached), and I want to analsye them both so need the data points to line up. Is there a code I can use to get Matlab to line up the data points for me? i.e the peak point for U should be the same data point as the one for D. The matrices are the same size but can be shortened if necessary to do this.
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Vilém Frynta el 23 de Mzo. de 2023
hello,
yes.
% make vectors from your data (previously columns)
U = U'
U = 1×2328
0.0043 0.0043 0.0045 0.0044 0.0047 0.0046 0.0047 0.0046 0.0051 0.0049 0.0050 0.0047 0.0048 0.0049 0.0048 0.0047 0.0046 0.0044 0.0043 0.0044 0.0049 0.0048 0.0046 0.0045 0.0047 0.0049 0.0046 0.0047 0.0046 0.0046
D = D'
D = 1×2328
0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0139 0.0140
% find maxs (peaks)
idx.U = find(U == max(U));
idx.D = find(D == max(D));
% difference between the peaks
idx.diff = idx.U - idx.D
idx = struct with fields:
U: 656 D: 398 diff: 258
% let's assume U is further
is_U_further = 1;
% find if D is further (if idx.diff is negative)
if idx.diff < 0
is_U_further = 0;
idx.diff = idx.D - idx.U % switch the difference in that case
end
% create NaN vector and new variables
L = length(U);
new.U = NaN([1 L+idx.diff]);
new.D = NaN([1 L+idx.diff]);
% fit the values so the peaks are at the same index
if is_U_further == 1; % if U is further... do this:
new.U(1:L) = U;
new.D(idx.diff:idx.diff+L-1) = D; % move D further, so it matches
end
if is_U_further == 0;% if D is further...
new.D(1:L) = D;
new.U(idx.diff:idx.diff+L-1) = U;
end
plot(new.U)
hold on
plot(new.D) thought i did it wrong but it looks like "D" is just too small (no pun intended). you can try to strech that or make new, relative Y axis for it.

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Mathieu NOE el 27 de Mzo. de 2023
hello
myabe this ?
I took the options to have both peaks overlaid and also the two curves have same initial y value
This is the result
of course you can change the code if your prefer to have same y final value but I doubt you can have start, end and peaks points all 3 overlaid
% find maxs (peaks)
[umax,iumax] = max(U);
[umin,iumin] = min(U);
% dU = umax- umin;
dU = umax- U(1);
[dmax,idmax] = max(D);
[dmin,idmin] = min(D);
% dD = dmax- dmin;
dD = dmax- D(1);
% D y dir stretch factor
D_ySt = dU/dD;
D = D*D_ySt;
% apply y shift to have both curves start at same value U(1)
yshift = D(1) - U(1);
D = D - yshift;
% x axis shift to align both peaks (delay D vs U)
xshift = iumax - idmax;
% define x axis vectors
xu = 1:numel(U)
xd = xu + xshift;
plot(xu,U,xd,D) ##### 0 comentariosMostrar -1 comentarios más antiguosOcultar -1 comentarios más antiguos

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