How to calculate PSNR in Matlab Figure file?

I wish to calculate the PSNR between two signals.

The input file would be Matlab Figure file.

signal1 = openfig('Figure1.fig');
signal2 = openfig('Figure2.fig');
[R C]=size(signal1);
err = sum((signal1-signal2).^2)/(R*C); 
MSE=sqrt(err);
MAXVAL=65535;
PSNR = 20*log10(MAXVAL/MSE); 
disp(MSE);
disp(PSNR);

However, the error shows:

Operator '-' is not supported for operands of type 'matlab.ui.Figure'.
Error in file (line 4)
err = sum((signal1-signal2).^2)/(R*C);

How can I solve the error?

Answer 1

[Mehmed Saad]

signal1 = openfig('Figure1.fig');
signal2 = openfig('Figure2.fig');

signal1 contains the figure handle not the data

you have to extract data from figure handle, you cannot directly subtract two figures data by subtracting there handle

to extract data from figure handle (assuming they contain 1 line only)

data1 = signal1.Children(1).Children(1).YData;
data2 = signal2.Children(1).Children(1).YData;

Now you can process data1 and data2 from here after

[Star Rats]

Thanks Sir @Muhammad Saad. It works.

However, is it possible to compare signals between mp3 file and wav file?

Figure1 is signal of mp3 file while Figure2 is signal of wav file.

Previous error mentioned above is solved. However, new error shown:

Matrix dimensions must agree.

Is there any method to standardize both signal so that psnr can be calculated?

Thank you.

[Mehmed Saad]

your matrix are not of same dimension.

There are two possible things in this contex which make there dimension different

1. sampling rate
2. time of signal

to get the time signal from plots

t1 = signal1.Children(1).Children(1).XData;
t2 = signal2.Children(1).Children(1).XData;

Now you have to check if their sampling rates are same or not and their ending times are same or not

1. if their sampling rate is same but ending time is not, truncate the longer time signal
2. f their time ends at the time then they have different sampling rate. you either have to upsample the low sampling signal or downsample the high sampling signal so that both signal are of same sampling rate
3. if ending time and sampling rate both are not matching, first match the time and then follow the step 2

Now you have to do it yourself. it is basic matrix operation.

[Star Rats]

Thanks @Mehmed !