Problems on using 'hamming' function

I am trying to use STFT with hamming command. Actually, it is working well on my PC, but not working on my co-worker's PC. I reinstalled MATLAB and tried again, but the problem has not been solved yet...

Here are the error messages :

Undefined variable "signal" or class "signal.internal.sigcasttofloat".

Error in gencoswin (line 15) n = signal.internal.sigcasttofloat(varargin{2},'double','gencoswin','N',...

Error in hamming (line 22) [w,msg,msgobj] = gencoswin('hamming',varargin{:});

Error in Bandpass_filter (line 22) window = hamming(PQRST_length);

Error in Main (line 35) Band_filtered_ECG = Bandpass_filter(Measured_ECG, Number_of_total_data);

Thank you

[Darshan Ramakant Bhat]

Please check if there is any other file named signal present in the MATLAB path by executing the below command:

which signal