# finding the error between two curves from a fig

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Paul Rogers on 19 Jul 2020
Commented: Paul Rogers on 19 Jul 2020
I have a fig, the onee in attaced (example).
Considering the green one the true value, how can I evaluete the error of the second?
P.S.
I have Matlab 2014b

#### 1 Comment

Paul Rogers on 19 Jul 2020
someone suggested this and theen deleted, but it's not working:
Open the figure and run the following commands to calculate the MSE .
% get current axes
ax = gca;
% get Y data of green and blue lines
GreenLineY = ax.Children(1).YData ;
BlueLineY = ax.Children(2).YData;
% MSE
MeanSquaredError = (GreenLineY - BlueLineY) .^2;

Takumi on 19 Jul 2020
I used the findall function to find out what was plotted.
I noticed that some of the lines containing the NaN values were plotted as nonsense.
The lines you're trying to compare are probably h(2) and h(6).
In addition, the blue line contains NaN values that need to be removed.
Finally, we need to align the number of elements to compute the error, so we interpolate.
% get current axes
ax = gca;
% find object
h = findall(ax);
% get Y data of green and blue lines
GreenLineX = h(2).XData;
GreenLineY = h(2).YData;
BlueLineX = h(6).XData;
BlueLineY = h(6).YData;
% eliminate NaN
BlueLineX = rmmissing(BlueLineX);
BlueLineY = rmmissing(BlueLineY);
% interpolation
GreenLineY_interp = interp1(GreenLineX,GreenLineY,BlueLineX,'spline');
% MSE
MeanSquaredError = mean((GreenLineY_interp - BlueLineY).^2);
figure
plot(GreenLineX,GreenLineY,'-g');
hold on
plot(BlueLineX,BlueLineY,'-b');

Takumi on 19 Jul 2020
Really? Your version is 2014b right?
Takumi on 19 Jul 2020
I have installed MATLAB version 2014b and it worked fine.
Paul Rogers on 19 Jul 2020
sorry, It works. I just did a very stuoid mistake!
You're great, thanks for helping me.

R2014b

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