How to add iteration in a string (make multiple strings using iterations without indexing) ?

I have been wondering for a loooong time how to acheive this. (I am a beginner by the way so please bear with me)

The problem is shown in the sample code below. I want the numerical "i" to be used in the string to output: "png1", "png2", and so forth.

Of course the code doesn't work.

I know of a way; to make a matrix in advance with string then access the matrix but this won't work with a while loop.

I thank you so much in advance.

for i = 1:4

matlab = "png(i)"

end

Answer 1

[the cyclist]

Here is one way:

for i = 1:4
    matlab = sprintf("png%d",i)
end

matlab = "png1"

matlab = "png2"

matlab = "png3"

matlab = "png4"

Here is another, but wanted to show the first way, which can be more versatile for other ways to build strings and/or character arrays.

for i = 1:4
    matlab = "png"+i
end

matlab = "png1"

matlab = "png2"

matlab = "png3"

matlab = "png4"

[Haisam Khaled]

I THANK YOU SO MUCH. I was going insane trying to figure this out.

I have something to say about second way, I was trying to add i as a char, I didn't think of adding it as a string, as changing a numerical to a string copys it.

Again, THANK YOU SO MUCH <3

[Image Analyst]

@Haisam Khaled, another way is to make a cell array of strings:

stringList = cell(4, 1); % Preallocate list of empty cells.
% Fill that list with strings (actually character arrays here,
% but you could do strings if you want).
for k = 1 : 4
    stringList{k} = sprintf('png%d', k) % Character array type.
    %stringList{k} = "png" + k; % String type
end

See the FAQ:

https://matlab.fandom.com/wiki/FAQ#What_is_a_cell_array.3F

[Steven Lord]

If you want to create a 4 element string array you don't need to use a loop. Adding a string scalar and a numeric vector converts the numeric vector to a string array of the same size then adds on that string scalar to each element. You can even use implicit expansion.

i = (1:4).';
matlab = "png"+i

matlab = 4×1 string array
    "png1"
    "png2"
    "png3"
    "png4"

y = matlab + i.'

y = 4×4 string array
    "png11"    "png12"    "png13"    "png14"
    "png21"    "png22"    "png23"    "png24"
    "png31"    "png32"    "png33"    "png34"
    "png41"    "png42"    "png43"    "png44"

[Image Analyst]

@Steven Lord, neat trick. Good to know. Thanks for sharing.

matlab is a reserved variable name so he should use a different variable name. Just type matlab on the command line then dot and and the tab key to see all the methods and properties of the matlab object/class. Another neat trick.

[Haisam Khaled]

@Image Analyst DUUUDE this was the one that started it all, I saw it once somewhere, but somehow forgot it and no matter what I tried, I never thought of this one. THANK YOU AGAIN, now I have immense knowledge <3

Answer 2

[Image Analyst]

If I understand you correctly you want to dynamically/programmatically create named variables and then access them later by that created name. The reasons against this are discussed in the FAQ:

https://matlab.fandom.com/wiki/FAQ#How_can_I_create_variables_A1.2C_A2.2C....2C_A10_in_a_loop.3F

[Haisam Khaled]

Hey man, first of all, I am a big fan of you, you answered many questions of other people that I benefitted a lot from.

Second, I know my mind is that of a beginner and yours is so advanced and much smarter than me. I didn't explain the problem well, regaardless someone understood my stupid explanation and provided a solution, I thank you soooo much for your effort.

P.S. this article was helpful <3