# Plotting matrices that don't have the same size

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Samy Ben Thabet am 29 Nov. 2018
Bearbeitet: Akira Agata am 30 Nov. 2018
I am trying to plot two matrices it doesn't work.
matrix_1 is a 181x1 matrix with different values, I am trying to plot these values and also get a line fitted on the same plot, I tried polyfit as well but it doesn't work.
Message diplayed:
"Error using plot
Vectors must be the same length."
x=1941:2010
y=matrix_1
plot(x,y)
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Bob Thompson am 29 Nov. 2018
Bearbeitet: Bob Thompson am 29 Nov. 2018
Yes, matlab is expecting coordinate pairs.
How is your data related? X appears to be years, but should there be one set of results for each year, or is there some other correlation?
Samy Ben Thabet am 29 Nov. 2018
Oh right my bad. I guess I made a mistake somewhere in my code I will try to fix that.
Thank you!

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### Antworten (1)

Ken Atwell am 30 Nov. 2018
When calling plot, the length of the x,y pairs must be equal. Here is an example of a plot of x^2 with noise added, then then a polyfit to that data:
x=-3:.1:3;
y=x.^2+rand(size(x));
f=polyfit(x, y, 2); % Returns coefficients, not y values directly
fy = f(1).*x.^2 + f(2).*x + f(3);
plot(x,y,x,fy)
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Akira Agata am 30 Nov. 2018
Bearbeitet: Akira Agata am 30 Nov. 2018
If these two matrices are not the same size but matrix_1 is a sampled data from x = 1941 to 2010 with some fixed sampling frequency, adjusting length of x with linspace function would be possible solution. Here is an example.
x = 1941:2010;
y = matrix_1;
xInterp = linspace(min(x),max(x),numel(y));
figure
plot(xInterp,y)

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