Using num2str with negative numbers

Question

Juan Jose Ortiz Torres 2019-2-28

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/447499-using-num2str-with-negative-numbers

评论： Star Strider 2019-3-13

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?

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Answer 1

Star Strider 2019-2-28

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/447499-using-num2str-with-negative-numbers#answer_363174

在 MATLAB Online 中打开

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.

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Answer 2

Juan Jose Ortiz Torres 2019-3-13

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/447499-using-num2str-with-negative-numbers#answer_365093

在 MATLAB Online 中打开

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

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Juan Jose Ortiz Torres 2019-3-13

在 MATLAB Online 中打开

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 2019-3-13

在 MATLAB Online 中打开

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 '}