Is there a simpler or more efficient way to do the following?

The assignment was to: "Write a program (function) that takes in an non-empty integer array A with unknown rows and columns and return an string matrix B with matrix A is padded at left hand side with row number followed by a tab character (char(9))and on top with column number"

The code I came up with and that seems to work is the following:

function B = label(A)
    %Function to label rows and columns in an array with numbers
    
    B = string(A);
    % sets B to the string version of the A array
    
    [~,columnsInB] = size(B);
    % gets the current size of our array
    
    insertRow = zeros(1,columnsInB);
    % creates a placeholder to use later in inserting a row
    
    rowToInsert = 1;
    % defines which row we will insert on
    
    columnToInsert = 1;
    % defines which column we will insert on
    
    B = [B(1:rowToInsert-1,:); insertRow; B(rowToInsert:end,:)];
    % set the string array B to a copy of it which has the extra inserted
    % row
    
    [rowsInB,~] = size(B);
    % gets new size of array
    
    insertColumn = zeros(rowsInB,1);
    % creates a placeholder to use later in inserting a column
    
     B = [B(:,1:columnToInsert-1), insertColumn, B(:,columnToInsert:end)];
    % set the string array B to a copy of it which has the extra inserted
    % column
    
    [rowsInB,columnsInB] = size(B);
    % gets new size of array
    
    B(1) = '    ';
    % sets the first value to nothing
    
    for rows = 2:rowsInB
        % loop to add row numbers to the first column with the indent
        B(rows) = (rows - 1+"    ");
    end
    
    for columns = 2:columnsInB
        % loop to add column numbers to the first row
        B(1, columns) = columns - 1;
    end
end

Answer 1

[J. Alex Lee]

You could for example do this

function B = label1(A)
[rows,cols] = size(A);
B = ["",string(1:cols);[string((1:rows)')+char(9),A]];
end

I don't claim that it is simpler/more efficient, nor the most compact. Mixed feelings on whether it is a useful learning/teaching snippet either.

Likely the hw problem was written before "strings" were actually a thing, and the answer saught is a character array. At least that would be the more interesting hw problem to pose imho.

[Terin Richardson]

definitely way more compact than my answer! the way I ended up doing it worked but doing it this way would be way faster. Thanks!

[Terin Richardson]

For some reason my brain isn't wrapping around how you formatted the string to get the result. Can you explain the the third line and what it is doing exactly?

[J. Alex Lee]

This line hides implicit type conversion and concatenation.

Concatenation:

[a,b]

is shorthand for horizontal concatenation

horzcat(a,b)

and

[c;d]

is shorthand for vertical concatenation

vertcat(c,d)

Implicit type conversion with operations on strings.

Try

3.1415 + ""

and you get the string

"3.1415"

so you implicitly converted the double 3.1415 into a string as if you did

string(3.1415)

You already used the above version in your original code when converting A.

So you can create a columnar string array of row numbers with implicit conversion

string((1:rows)')+char(9)

and just concatenate with A, which also leads to implicit conversion of A into string(A).

C = horzcat(string((1:rows)')+char(9),A)

that's the "inner" concatenation with the square brackets.

Now you can make the header using the same principles

H = horzcat("",1:cols)

So you didn't even really need the string() around 1:cols.

Then

B=vertcat(H,C)

or you can do it one shot using square brackets