fprintf command issue. tricky columns.

a=1:5;
b=90:94;

fprintf('Variables A : %.f  |  Variables B : %.f\n',a,b);

Consider the script above.

Variable a are the small values. I want to print all the variables on the LEFT COLUMN. Then variable b on the RIGHT column.

However with this sequence of fprintf the variable a results in an entirely different order.

1 2
3 4
5 90
91 92
93 94

Answer 1

[Honglei Chen]

The trick is [a;b], like this

fprintf('Variables A : %.f  |  Variables B : %.f\n',[a;b]);

[Sara Pierson]

THIS WORKED FOR ME! Thank you! (I am using matlab 2020b btw if that helps anyone else)

Answer 2

[Burners]

What i want is, the same style as my vectors are arranged

1   90
2   91
3   92
4   93
5   94

[Walter Roberson]

Honglei's technique is the correct one when you are starting with row vectors:

fprintf('%f %f\n', [a;b])

If you are starting with column vectors then

fprintf('%f %f\n', [a,b].')

[Margs V]

I have the exact same problem as Burners. Even when using the code as suggested in this answer it seems that Matlab takes the first column of the data and fills all the available slots in the first few rows of the .txt file, then moves on to the second column etc. In other words the data is read from the variable column by column and added to the .txt file row by row.

For example: a matrix has [1 2 3 ; 1 2 3 ; 1 2 3; 1 2 3], but it is written to my text file as [1 1 1; 1 2 2; 2 2 3; 3 3 3].

I want to have an output file that has the same structure as the data.

[Walter Roberson]

>> M = [1 2 3 ; 1 2 3 ; 1 2 3; 1 2 3]
M =
     1     2     3
     1     2     3
     1     2     3
     1     2     3
>> fprintf('%f %f %f\n', M.');  %notice the transpose
1.000000 2.000000 3.000000
1.000000 2.000000 3.000000
1.000000 2.000000 3.000000
1.000000 2.000000 3.000000

[Diaa]

why is it not written in the documentation? or was it?

[Walter Roberson]

https://www.mathworks.com/help/matlab/ref/fprintf.html

fprintf(fileID,formatSpec,A1,...,An) applies the formatSpec to all elements of arrays A1,...An in column order, and writes the data to a text file.

If you have R2016b or later you might also want to look at compose(), which does not have this same behaviour.

[Rik]

The fundamental point is that Matlab arrays are column-based. We might read row by row when we look at an array to be written, but Matlab doesn't. Maybe there should be a warning to this effect in the doc, but as far as I'm aware there isn't. If you want to avoid ambiguous situations, you should provide each input as a separate array.