CODEWITHSUNDEEP
matlabgraphplot
Didii
Didii

Reputation: 1363

Plot a peak with height

How can I properly plot a peak in Matlab with a given height? My current method:

x = linspace(0,500,500);
peaks = zeros(size(x));
peaks(50) = 5;
peaks(300) = 20;
peaks(302) = 17;
peaks(375) = 15;
plot(x,peaks)

which gives

Peaks

But this is ugly, confusing when multiple lines are close and leads to problems when converting it to a log scale since log(0)=-Inf. Is there a proper way of plotting peaks?

Context: I'm trying to analyse a spectogram (EDXS) to identify which material I'm working with.

Upvotes: 0

Views: 153

Answers (2)

Daniel
Daniel

Reputation: 36710

Scaling the scale to log, you are asking Matlab to draw a line between -Inf and a positive value. Such lines are skipped.

To get a usable log plot, use points instead of lines:

plot(x,peaks,'x')

Another nice possibility to plot peaks is a stem-plot

enter image description here

Upvotes: 1

Stewie Griffin
Stewie Griffin

Reputation: 14939

I think the reason why you only get single pixels in your log-plot is because most of your values are 0. As log(0) = -Inf, this can't be plotted.

I know nothing of spectogram analyses, but if you absolutely want to plot this with a logarithmic scale, is it possible to use a "base line" equal 1 (0 in a log scale). If so:

x = linspace(0,100);
peaks = ones(size(x));
peaks(10) = 5;
peaks(60) = 20;
peaks(75) = 15; 
semilogy(x,peaks)

enter image description here

I guess that this will look more reasonable with your real data. Note: If you have values that are less than 1, I would not go with this approach!

Upvotes: 0

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