fprintf in a for loop printing repetitive answers in command window

Hi i'm working on a function that selects the peaks from a data and prints the coordinates of each peak. Also it marks the peaks in a plot.

When I run the program the plot looks great but there are repetitive answers in the Matlab command window. My program is the following:

clear all
close all
clc

n=10;
b = randn(n,1);
a = cumsum(b);
da = diff(a);

plot(a); 
hold on;

i=1;

if da(i) < 0
    harm = a(i);
    freq = i;
    plot(freq,harm,'ro');
    hold on
    fprintf('Harmonic of Amplitude %.2f at %d Hz\n',harm,freq) 
    i = i + 1;
end

for i = i:n-1
    while i < n-1 
    if ((da(i) > 0) && (da(i+1) < 0))
        harm = a(i+1);
        freq = i+1;
        plot(freq,harm,'ro');
        hold on
        fprintf('Harmonic of Amplitude %.2f at %d Hz\n',harm,freq)
        i = i + 1;
    else i = i + 1;
    end
    end
end

if da(n-1) > 0
    harm = a(n);
    freq = n;
    plot(freq,harm,'ro');
    hold on
    fprintf('Harmonic of Amplitude %.2f at %d Hz\n',harm,freq) 

end

The command window give this results:

Harmonic of Amplitude 0.57 at 1 Hz Harmonic of Amplitude -0.19 at 9 Hz Harmonic of Amplitude -0.19 at 9 Hz Harmonic of Amplitude -0.19 at 9 Hz Harmonic of Amplitude -0.19 at 9 Hz Harmonic of Amplitude -0.19 at 9 Hz Harmonic of Amplitude -0.19 at 9 Hz Harmonic of Amplitude -0.19 at 9 Hz

What it happening that the program gives the results repeated?

[Jiro Doke]

Can you edit this question and use appropriate formating. Highlight the text that represents MATLAB code, and click on the {}Code button.

Answer 1

[Sean de Wolski]

Your values: harm, freq are probably not scalars and thus it's printing multiple times to show all contents.

Use

 num2str(harm)

and the %s operator to show both values in one location. e.g.

 fprintf('Hello World: %s\n',num2str(harm))
 %SCd

Answer 2

[Matt Tearle]

Your code is hard to read b/c of the formatting, but it seems to me that you're trying to do something very similar to this other answer. In which case... can I suggest a much neater version, that also isn't producing repeat display lines (at least not for me):

n=10; b = randn(n,1); a = cumsum(b); da = diff(a);

idx = [da(1)<0; da(2:end)<0 & da(1:end-1)>0; da(end)>0];
nmax = find(idx);
amax = a(idx);
plot(1:n,a,'o-',nmax,amax,'rx')

fprintf('Harmonic of Amplitude %.2f at %d Hz\n',[amax';nmax'])