Help with Smooth graph interpolation

I have two columns of data imported from excel in workspace labelled as "Sample 1". How can I take those columns and make a smooth graph? They are both 88 rows long with column 1 being my X values and column 2 being my Y values. Thank you!

Answer 1

[Star Strider]

I have no idea what your data are, and I am not certain what defines ‘smooth’.

With that proviso, try this:

xq = linspace(min(Sample_1(:,1)), max(Sample_1(:,1)), numel(Sample_1(:,1))*10);
yq = interp1(Sample_1(:,1), Sample_1(:,2), xq', 'pchip');

figure
plot(Sample_1(:,1), Sample_1(:,2), 'xb')
hold on
plot(xq, yq, '-r')
hold off
grid

Experiment with the interp1 function 'method' arguments to get different results.

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[Eric Yoshida]

Hmm I'm getting this error message "Error using min

Invalid data type. First argument must be numeric or logical."

[Star Strider]

Apparently, ‘Sample_1’ is not numeric. I need to know what it is to help.

[Eric Yoshida]

The variable is called Samples106 with column 1 in the data set being labelled "strain" and column 2 being labelled "Column1". Both columns start with 0 and continue in an increasing, non-linear order for 88 rows. Is that what you are looking for or is it something else?

[Star Strider]

Something else. It could be a cell array, in which case it would require different indexing. The easiest way to solve this would be for you to attach it as a .mat file.

[Eric Yoshida]

Hopefully this helps. Sorry for the confusion!

[Star Strider]

No worries!

The ‘y’ field (the one that matches your description) is a table. It requires a bit of code to get its data.

Experiment with this:

D = load('Graph data.mat');
y = D.y;

vx = y.Column1;
vy = y.strain;

mult = 0.25;
xq = linspace(min(vx), max(vx), numel(vx)*mult);
yq = interp1(vx, vy, xq', 'pchip');

figure
plot(vx, vy, 'xb')
hold on
plot(xq, yq, '-r')
hold off
grid

Change the value of ‘mult’ and the interp1 'method' (here, 'pchip') to get the result you want.

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