replacing numbers with text

Hello everyone,

I want to replace text with numbers. 1=s, 3=r, 4=b . I tried 2 methods. Cant figure why niether of the codes wont work . What am I doing wrong?

% Method 1 / not working returns "Index exceeds the number of array elements (3)." error 
mymat= [ 4     4     4
         3     4     4
         1     4     4
         4     3     4
         3     3     3
         1     3     4
         4     1     4]
t = string(["b", "r", "s"])
comMat = t(mymat)


%Method 2 / returns a NaN matrix and that's not what I want. 
mymat= [ 4     4     4
         3     4     4
         1     4     4
         4     3     4
         3     3     3
         1     3     4
         4     1     4]
mymat(mymat==4)= "b"
mymat(mymat==3)= "r"
mymat(mymat==1)= "s"
mymat

thank you for your time in advance.

Answer 1

[Adam Danz]

Here's a more flexible alternative.

mymat= [ 4     4     4
         3     4     4
         1     4     4
         4     3     4
         3     3     3
         1     3     4
         4     1     4];
t = ["s", "r", "b"];
v = unique(mymat(:));  % or maybe you want unique(mymat(:),'stable')
B = string(categorical(mymat,v,t))

B = 7×3 string array
    "b"    "b"    "b"
    "r"    "b"    "b"
    "s"    "b"    "b"
    "b"    "r"    "b"
    "r"    "r"    "r"
    "s"    "r"    "b"
    "b"    "s"    "b"

Also works for any values

mymat(mymat==4) = 10;
mymat(mymat==1) = -42.5

mymat = 7×3

10.0000 10.0000 10.0000 3.0000 10.0000 10.0000 -42.5000 10.0000 10.0000 10.0000 3.0000 10.0000 3.0000 3.0000 3.0000 -42.5000 3.0000 10.0000 10.0000 -42.5000 10.0000

●

B = string(categorical(mymat, unique(mymat(:)), ["s", "r", "b"]))

B = 7×3 string array
    "b"    "b"    "b"
    "r"    "b"    "b"
    "s"    "b"    "b"
    "b"    "r"    "b"
    "r"    "r"    "r"
    "s"    "r"    "b"
    "b"    "s"    "b"

Another alternative

B= discretize(mymat, [unique(mymat(:));inf], ["s", "r", "b"])

B = 7×3 string array
    "b"    "b"    "b"
    "r"    "b"    "b"
    "s"    "b"    "b"
    "b"    "r"    "b"
    "r"    "r"    "r"
    "s"    "r"    "b"
    "b"    "s"    "b"

[klb]

Works! Thank you Adam for the solutions and your time.

Answer 2

[Image Analyst]

Well here's one way. Using a simple for loop

mymat= [ 4     4     4
	3     4     4
	1     4     4
	4     3     4
	3     3     3
	1     3     4
	4     1     4]
t = string(["b", "", "r", "s"])
[rows, columns] = size(mymat)
for col = 1 : columns
	for row = 1 : rows
		output(row, col) = t(mymat(row, col));
	end
end
output % Show in command window.

I'm sure other people will show you other ways.

Answer 3

[Jose]

The easiest is to replace the numbers by ASCII codes corresponding to your letters and then convert to char. You can index each character as a normal matrix i.e. comMAT(1,1)

I have edited the answer to make it generic

comMAT=nan(size(mymat));
comMAT(mymat==4)=98;
comMAT(mymat==3)=114;
comMAT(mymat==1)=115;

comMAT=char(comMAT);

[Stephen23]

Nice and simple, but has the disadvantage that it requires hard-coding each value separately, it could be looped to avoid that.

Important: this works because the output array is distinct from the input array. Note that the char conversion can be applied on the first line.

[Jose]

I was assuming the objective was replacing single digit int by alphanumerical. That piece of code does that in a simple way. It can be very easily generalized if the output matrix comMAT is initialized to NaN and the transformation is done there. For a lot of values it will require a for loop that in that case is not very elegant solution, I agree.