printing string (from a cell array) and double array with fprintf

got the following variables: lab is a cell array and vec_var is a double array

fprintf('%s\n', lab{:})
BHP
NAB
CSR
AGL
NCP
fprintf('%.4g\n', vec_var)
0.000324
0.000256
0.000484
0.001296
0.002304

trying to print as follows:

BHP = 0.000324
NAB = 0.000256
CSR = 0.000484
AGL = 0.001296
NCP = 0.002304

Tried several different fprintf statements, none give the output I want:

 fprintf('%s\t = \t%.4g\n ', lab{:}, vec_var);
  BHP   =   78
   AB   =   67
   SR   =   65
   GL   =   78
   CP   =   0.000324
   2.560000e-04   =   0.000484
   1.296000e-03   =   0.002304

so far only the following came close:

for j=1:length(lab)
    fprintf('%s = \t ', lab{j});
    fprintf('%.4g', vec_var(j));
end

BHP =    
0.000324
NAB =    
0.000256
CSR =    
0.000484
AGL =    
0.001296
NCP =    
0.002304

but with extra new lines (why?)

What's the best way to do this?

Thanks! Yudi

Answer 1

[Walter Roberson]

var_vec_cell = num2cell(vec_var);

data = [lab(:), var_vec_cell(:)] .';    %transpose is important

fprintf('%s\t = \t%.4g\n ', data{:})

[yudi vass]

Thanks for the code. I am still not sure how fprintf works when handling two arrays. When using just one array it loops and prints each element fine but when combined the behavior is hard to figure out. Why is transpose important?

[Guillaume]

The data{:} expansion in Walter's answer is equivalent to:

fprintf(%s\t = \t%.4g\n ', data{1}, data{2}, data{3}, ..., data{end})

fprintf just feeds its inputs in order to the formatting codes. If there's more input arguments than formatting codes, it just restart from the start of the format string until it's consumed all inputs.

Therefore you want data{1} to be lab{1}, data{2} to be var_vec_cell{1}, data{3} to be lab{3}, etc. The concatenation plus transpose just ensures that you obtain this mapping.

Another way of creating data would be:

data = [reshape(lab, 1, []); reshape(var_vec_cell, 1, [])];

Walter's way is just less characters to type (at the expense of more reshaping/transposition)

[Jon Martinez]

I know this is quite an old answer but I just wanted to say this post is pure gold. For the longest time I thought the only way to combine numbers and string with fprintf was with a loop and never ocurred to me to use cells. Hats off Mr. Roberson.

[Paul Martin]

I agree with Jon that the post is pure gold.

Nevertheless it is worth while to point out that from R2016b you can use

compose

to get very similar functionality. I point this out because compose does not seem to be very well known: there are plenty of questions to uncle Google about sprintf and cell arrays but very few answers (none that I can find) mention compose.