Thinking in matrices in Matlab

Question

Let's take a simple example. I am trying to change my way of thinking to get more matrix oriented.

I have data

epsilonM = [0.001 10*h h 0];
situations = ['i.a)' 'i.a)' 'i.Q' 'ii.:w']; 
hleg = legend(sprintf('%s Epsilon = %d, \n', situations, epsilonM));

I would like to get output

i.a) Epsilon = 0.001
i.a) Epsilon = 10*h,
i.Q Epsilon = h,
i.b) Epsilon = 0,

but I get

enter image description here

I have an intuition that there is a better way to do this - component wise.

How can you achieve the result without use of for loops, only by matrices?

For a 4 line string manipulation, I would use a loop. Your output is all garbled it's printing the 4 elements of situations, then the next part of your string "Epsilon = ", then the 4 elements of epsilonM. This behavior of s/fprintf is expected, but I've never found a good use for it. — Frederick
– Frederick, Commented Oct 14, 2013 at 21:55

Luis Mendo · Accepted Answer · 2013-10-14 21:53:42Z

3

In this case it's easier with cell arrays:

situations = {'i.a)' 'i.a)' 'i.Q' 'i.b)'};
epsilonM = {'0.001' '10*h' 'h' '0'};
aux = strcat(situations, {' Epsilon = '}, epsilonM);
legend(aux);

Note that the curly braces in {' Epsilon = '} are only necessary to prevent strcat from removing trailing white space (see doc of strcat)

answered Oct 14, 2013 at 21:53

Luis Mendo

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3 Comments

Léo Léopold Hertz 준영 Over a year ago

I use also epsilonM as data source. Is there any possibility of change int2str() there somehow? Or should I have two vars?

Luis Mendo Over a year ago

@Masi You probably need two vars. You could do num2str on your numeric variable epsilonM, but you would get the numbers converted to strings, never an h as part of the strings

Luis Mendo Over a year ago

@Masi Now that I think about it: you could divide your numeric vector epsilonM by h. So strcat(num2str(epsilonM(:)/h),'h') could generate the desired string representation of epsilonM. Note that the (:) is necessary to turn epsilonMinto a column vector, as num2str gives one result per row. Finally, use this to concat everything: strcat(situations.', {' Epsilon = '}, strcat(num2str(epsilonM(:)/h),'h'))

Daniel · Accepted Answer · 2013-10-14 21:55:13Z

2

Check the output of this line:

situations = ['i.a)' 'i.a)' 'i.Q' 'ii.:w'];

This is a single char of size 1 16, not the array you intended. I would recommend to use a cell:

situations = {'i.a)' 'i.a)' 'i.Q' 'ii.:w'};.

Thus:

epsilonM = [0.001 10*h h 0];
situations = {'i.a)' 'i.a)' 'i.Q' 'ii.:w'}; 
hleg = legend(sprintf('%s Epsilon = %d, \n', situations{:}, epsilonM));

answered Oct 14, 2013 at 21:55

Daniel

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