How can I improve speed of strcat in a for loop?

I am new to MATLAB and am trying to turn the constitution into binary.

When I run the code below, It takes around a minute to run. Having tested it with the strcat part commented out the code runs fairly fast so I believe the concatenation part of the code is the slower part.

I attempted to pre-allocate an array of chars that is 7 times the length of the constitution file in order to increase the speed of the for loop but this didn't work and produced incorrect results. Below is the code I attempted to use:

file = fopen('constitution.txt');
constitution = fscanf(file,'%c');

Asc = cell(1,length(constitution));
code = char(zeros(1,length(constitution)*7)); %attempt at speeding up was unsuccesful and slowed down code/produced incorrect results
%code = ''; Original code, produced correct results but was very slow.

for i = 1:length(constitution)
    Asc{i} = dec2bin(constitution(i),7);
    code = strcat(code,Asc{i});
end

fclose(file);

My question I guess then is how can I correctly allocate the string in order to not have the variable 'code' be resized each iteration and hopefully speed up the code in the process.

Answer 1

[James Tursa]

Do you need "code" inside the loop for some reason? If not, why not construct it once outside the loop? E.g., something like this

Asc = cell(1,length(constitution));
for i = 1:length(constitution)
    Asc{i} = dec2bin(constitution(i),7);
end
code = strcat(Asc{:});  % concatenate everything at once

Or maybe this is all you need to do?

code = reshape(dec2bin(constitution,7)',1,[]);

[Logan Davis]

Wow, Thank you so much that worked very wonderfully and for some reason I didn't even think of that. Thanks for the quick reply and I hope you have a great day.