Understanding the following lines of code

Hello all, I am trying to understand the meaning of following two lines of code, but not getting it clearly.

file_x_train = strcat( file_px, num2str(ii),'_M',num2str(M), '_N',num2str(N),'_', num2str(SNRdB),'dB.mat' );
file_h_train = strcat( file_py, num2str(ii),'_M',num2str(M), '_N',num2str(N),'_', num2str(SNRdB),'dB.mat' );

where, M = number of antennas, N = number of elements, SNRdB is a constant value say 10 decibels.

Any help in this regard will be highly appreciated.

[Dyuman Joshi]

What are you facing difficulty with?

Did you check the documentation of strcat (and other functions used) and the output produced by the command above?

[chaaru datta]

Thanks a lot sir for your response...I had checked the strcat command and know that it is useful for concatenation....But I am getting confused due to use of ii, _M, dB.mat

[Stephen23]

A much better approach is to use SPRINTF.

M = 5;
N=10;
SNRdB = 10;
file_px = 'rawDatafileName';
ii = 2;

Compare:

sprintf('%s%d_M%d_N%d_%ddB.mat',file_px,ii,M,N,SNRdB)

ans = 'rawDatafileName2_M5_N10_10dB.mat'

strcat( file_px, num2str(ii),'_M',num2str(M), '_N',num2str(N),'_', num2str(SNRdB),'dB.mat' )

ans = 'rawDatafileName2_M5_N10_10dB.mat'

[chaaru datta]

Thanks a lot sir for your detailed response....

Answer 1

[akshatsood]

HI @chaaru datta,

Based on my interpretation of your question, it appears you are requesting insight into the "strcat" function. From the code sample you have ve shared, it is being used to construct a filename for a MAT file by connecting together different segments, where 'M' and 'N' represent the number of antennas and elements, respectively.

file_x_train = strcat( file_px, num2str(ii),'_M',num2str(M), '_N',num2str(N),'_', num2str(SNRdB),'dB.mat' );
file_h_train = strcat( file_py, num2str(ii),'_M',num2str(M), '_N',num2str(N),'_', num2str(SNRdB),'dB.mat' );

To break it down consider each argument to the "strcat" function

1. file_px - might be a file name (assuming file_px stores the file name 'file_px') => 'file_px'
2. num2str(ii) - casts number (stored in variable "ii") to character array (assuming 0 as it is not given) => '0'
3. '_M' => '_M'
4. num2str(M) - converts M to character array (assuming 20 as it is not given) => '20'
5. '_N' => '_N'.
6. num2str(N) - converts N to character array (assuming 5 as it is not given) => '5'
7. '_' => '_'
8. num2str(SNRdB) - converts SNRdB to character array (which is 10 as provided) => '10'
9. 'dB.mat' => 'dB.mat'

Hence, "strcat" function will concatenate all the strings(in monospace at the end of each point) and store the result in the respective variables "file_x_train" and "file_h_train".

Hence, the variable file_x_train = file_px0_M20_N5_10dB.mat

I hope this helps.

[chaaru datta]

Thank u sir for your answer...

Answer 2

[Aquatris]

My guess is the code is used to generate a name for a mat file after performing some postprocessing on raw data from 'file_px'.

So file_px is probably an excel sheet with data in it. Then probably some post-processing is done on the data from the excel sheet and the results needs to be saved. To have a meaningful name with the origin of the data, and some usefull info, they use the code. So just from the name of the mat file, you can see the info for _M SNR etc.,

M = 5;N=10;SNRdB = 10; % dummy postprocessed info from
file_px = 'rawDatafileName'; % dummy file name
ii = 2;
strcat( file_px, num2str(ii),'_M',num2str(M), '_N',num2str(N),'_', num2str(SNRdB),'dB.mat' )

ans = 'rawDatafileName2_M5_N10_10dB.mat'

So results show you that mat file contains data from 'rawDatafileName', has 5 antennas (_M5), has 10 elements (_N10) and has a SNR of 10dB (_10dB);

[chaaru datta]

Thanks a lot sir for your well written response...