Using num2str with negative numbers

Hi, i'm working with num2str but I can't get a coherent matlab answer.

if the numeros matrix doesn't have a negative number it works like the following

clear all
clc

numeros=[1.5 3.4 5.3 7.2;
         2.5 4.6 6.5 8.7];

parametro_numero_datos  = ['N' num2str(length(numeros),'%d')]


j=0;
for i = 0 : 2 : length(numeros)+2

        requestID(i+1,:) = ['i' num2str(numeros(1,j+1),'%-5.2f')];
        requestID(i+2,:) = ['d' num2str(numeros(2,j+1),'%-5.2f')];
j=j+1;

end

requestID

the answer is:

parametro_numero_datos =

    'N4'


requestID =

  8×5 char array

    'i1.50'
    'd2.50'
    'i3.40'
    'd4.60'
    'i5.30'
    'd6.50'
    'i7.20'
    'd8.70'

but if i have a negative number in the numeros matrix, it doesn't work

    clear all
clc

numeros=[1.5 -3.4 5.3 7.2;
         2.5 4.6 6.5 8.7];

parametro_numero_datos  = ['N' num2str(length(numeros),'%d')]

% requestID  = ['i' num2str(numeros(1,1),'%.4f')]
% requestID  = ['d' num2str(numeros(2,1),'%.4f')]

j=0;
for i = 0 : 2 : length(numeros)+2

        requestID(i+1,:) = ['i' num2str(numeros(1,j+1),'%-5.2f')];
        requestID(i+2,:) = ['d' num2str(numeros(2,j+1),'%-5.2f')];
j=j+1;

end

requestID

and the answer is:

parametro_numero_datos =

    'N4'

Unable to perform assignment because the size of the left
side is 1-by-5 and the size of the right side is 1-by-6.

Error in Concatenacion_string_numero (line 15)
        requestID(i+1,:) = ['i'
        num2str(numeros(1,j+1),'%-5.2f')];
 
>> 

colud you please help me?

Answer 1

[Star Strider]

It is best to go with cell arrays here:

j=0;
for i = 0 : 2 : length(numeros)+2
        requestID{i+1} = ['i' num2str(numeros(1,j+1),'%-5.2f')];
        requestID{i+2} = ['d' num2str(numeros(2,j+1),'%-5.2f')];
j=j+1;
end

although using the sprintfc (undocumented) or the compose (link) function would be your best option, avoiding the loop entirely:

i = 0 : 2 : length(numeros)+2;
requestID(i+1) = sprintfc('i%-5.2f', numeros(1,:));
requestID(i+2) = sprintfc('d%-5.2f', numeros(2,:));

similarly:

i = 0 : 2 : length(numeros)+2;
requestID(i+1) = compose('i%-5.2f', numeros(1,:));
requestID(i+2) = compose('d%-5.2f', numeros(2,:));

Experiment to get the result you want.

Answer 2

[Juan Jose Ortiz Torres]

Ok, but I does not work. Could you please give me all the correct code?, because I tried but it failed again even both ways.

I run the following:

clear all
clc

numeros=[1.5 3.4 5.3 7.2;
         2.5 4.6 6.5 8.7];

parametro_numero_datos  = ['N' num2str(length(numeros),'%d')]

% requestID  = ['i' num2str(numeros(1,1),'%.4f')]
% requestID  = ['d' num2str(numeros(2,1),'%.4f')]

j=0;
for i = 0 : 2 : length(numeros)+2

        requestID(i+1) = sprintfc('i%-5.2f', numeros(1,:));
        requestID(i+2) = sprintfc('d%-5.2f', numeros(2,:));
j=j+1;

end

requestID

the answer was:

parametro_numero_datos =

    'N4'

Unable to perform assignment because the indices on
the left side are not compatible with the size of the
right side.

Error in Concatenacion_string_numero (line 15)
        requestID(i+1) = sprintfc('i%-5.2f',
        numeros(1,:));
        
        

then, I tried with:

        clear all
clc

numeros=[1.5 3.4 5.3 7.2;
         2.5 4.6 6.5 8.7];

parametro_numero_datos  = ['N' num2str(length(numeros),'%d')]

% requestID  = ['i' num2str(numeros(1,1),'%.4f')]
% requestID  = ['d' num2str(numeros(2,1),'%.4f')]

j=0;
for i = 0 : 2 : length(numeros)+2

        requestID(i+1) = compose('i%-5.2f', numeros(1,:));
        requestID(i+2) = compose('d%-5.2f', numeros(2,:));
j=j+1;

end

requestID

And it does not work

parametro_numero_datos =

    'N4'

Unable to perform assignment because the indices on
the left side are not compatible with the size of the
right side.

Error in Concatenacion_string_numero (line 15)
        requestID(i+1) = compose('i%-5.2f',
        numeros(1,:));
 
>> 

HELP please

[Juan Jose Ortiz Torres]

I got the correct one:

clear all
clc

numeros=[1.5 -3.4 5.3 7.2;
         2.5 4.6 6.5 8.7];

parametro_numero_datos  = ['N' num2str(length(numeros),'%d')]

% requestID  = ['i' num2str(numeros(1,1),'%.4f')]
% requestID  = ['d' num2str(numeros(2,1),'%.4f')]

j=0;
for i = 0 : 2 : length(numeros)+2
        requestID(i+1,:) = sprintfc('i%-5.2f', numeros(1,j+1));
        requestID(i+2,:) = sprintfc('d%-5.2f', numeros(2,j+1));

j=j+1;

end

requestID

The output is

parametro_numero_datos =

    'N4'


requestID =

  8×1 cell array

    {'i1.50 '}
    {'d2.50 '}
    {'i-3.40'}
    {'d4.60 '}
    {'i5.30 '}
    {'d6.50 '}
    {'i7.20 '}
    {'d8.70 '}

[Star Strider]

Don’t use a loop. Just do this:

numeros=[1.5 -3.4 5.3 7.2;
         2.5 4.6 6.5 8.7];
     
i = 0 : 2 : length(numeros)+2;
        requestID(i+1) = sprintfc('i%-5.2f', numeros(1,:));
        requestID(i+2) = sprintfc('d%-5.2f', numeros(2,:));   

Then:

        Result = requestID

produces:

Result =

  1×8 cell array

  Columns 1 through 7

    {'i1.50 '}    {'d2.50 '}    {'i-3.40'}    {'d4.60 '}    {'i5.30 '}    {'d6.50 '}    {'i7.20 '}

  Column 8

    {'d8.70 '}