Converting integer values to logical array

I have a vector (160,1) in size which include integer number from 1 to 4, I want to convert in logical array by replacing 1 to(1 0 0 0), 2 to (0 1 0 0), and so on; for classifiction propblem.

Answer 1

[Image Analyst]

Try this:

m = randi([1, 4], 160, 1)
% Get 3 bit array
characterArray = dec2bin(m)
% Tack on column of 0's to the left edge
characterArray = [repmat('0', 160, 1), characterArray]
logicalArray = logical(characterArray - '0')

[Image Analyst]

I created a "a vector (160,1) in size which include integer number from 1 to 4" just like you said. Apparently you're starting with something else. Please give your code where you create that column vector.

[Najiya Omar]

it works perfectly now, i just create differnt size vector to test it, and I forgot to change it in the code.

thanks

[Image Analyst]

To be more robust for different sized vectors, use size() or length() when you call repmat():

m = randi([1, 4], 160, 1)
% Get 3 bit array
characterArray = dec2bin(m)
% Tack on column of 0's to the left edge
characterArray = [repmat('0', length(m), 1), characterArray]
logicalArray = logical(characterArray - '0')

[Najiya Omar]

thank you, it's really help

[Carlos Orduno]

Thanks for sharing,

This solution gave an error, so I modified it slighly, just in case someone is having any problem.

% Generate random values

m = randi([1, 4], 160, 1)

% Get 4 bit array

characterArray = dec2bin(m,4)

% convert to logical array

logicalArray = logical(characterArray - '0')

Answer 2

[Steven Lord]

You can use implicit expansion.

>> r = randi(4, 10, 1); % Your values will vary
>> values = r == 1:4;
>> t = table(r, values)

t =

  10×2 table

    r              values          
    _    __________________________

    1    true   false  false  false
    2    false  true   false  false
    3    false  false  true   false
    4    false  false  false  true 
    4    false  false  false  true 
    1    true   false  false  false
    4    false  false  false  true 
    4    false  false  false  true 
    2    false  true   false  false
    4    false  false  false  true 

Answer 3

[Anthony Bartoletti]

I'm not sure this is the answer requested. The solution given turns

1 into ( 1 0 0 0 ), 2 into ( 0 1 0 0 ), 3 into ( 1 1 0 0 ), 4 into ( 0 0 1 0 ).

But for a classification problem, you want to turn

1 into ( 1 0 0 0 ), 2 into ( 0 1 0 0 ), 3 into ( 0 0 1 0 ), 4 into ( 0 0 0 1 ).

I managed a solution: Create a logical 4x4 identity matrix with I = logical(eye(4)). Then given a sequence (row) r of integers 1 <= n <= 4, conduct

M = I( :, r)

This will select from the 4 logical basis vectors as columns, according to the sequence r.

Answer 4

[Deryck Chan]

I've combined the two approaches above and came up with this rather elegant solution:

% Example input
y = [1 3 4 5 7 9 8 2 1 5 10 3 4 6 8 2 6 1 2 7 10];
num_labels = max(y)

% Convert y into y_matrix
logic_template = eye(num_labels);
y_matrix = logic_template(:, y);

You can use boolean(eye(num_labels)) instead of eye(num_labels) if you want the result to be in the logical datatype.