fprintf command output and extra output

I am trying to change a sound file to ouput an echo.I have to output a column vector of size [4 1]. My output is:

output=echo_gen([-.5;0;.5;0],1,0,.5)
output =
     -0.7500
         0
    0.7500
         0

However, this is incorrect. I think it needs to be outputing like this:

output=echo_gen([-.5;0;.5;0],1,0,.5)
output =
     -0.75
         0
         0.75
         0
         

I tried using the fprintf('%g',output) and fprintf('%.2f',output) to remove the trailing zeros, but when i do that, i get this:

         output=echo_gen([-.5;0;.5;0],1,0,.5)
-0.75
0
0.75
0
output =
    15

Where is the output=15 coming from, and how do i remove it to get only the colum vector?

Thanks in advance.

Answer 1

[Stephen23]

You used the wrong operator. If you want to print to string, use sprintf.

"Where is the output=15 coming from..."

The fprintf documentation clearly describes that its only output is "Number of bytes that fprintf writes, returned as a scalar", which in your case also corresponds to characters on each line: 5 + 1 + 4 + 1 + 4(newlines) = 15.

"...and how do i remove it to get only the colum vector?"

Just suppress the function output using a semi-colon:

output=echo_gen(...);
                    ^ you need this!

But as mentioned at the start of my answer, I suspect that you really want to be using sprintf, not fprintf, as you indicate that you want to print text to an output argument.

[Jack Crespo]

Thanks Stephen! Im a junior in high school, and i am taking an online course, and this was one of the assignments. I actually was doing part of the problem incorrectly, and i needed to add some more logic in my code to get it working. But your explanation of fprintf and sprintf cleared up a lot of confusion I had, so thank you very much!