MATLAB Answers

How to overlay a log-plot on top of an image

33 ビュー (過去 30 日間)
Knut
Knut 2013 年 3 月 26 日
コメント済み: Scott Webster 2015 年 2 月 19 日
Here is the use-case: You have access to an image of a MATLAB semilogx() plot from a paper, a website or something similar. The original data are not easily available. You want to manually approximate the original vector. If one could overlay a local MATLAB semilogx() plot on top of the figure, that would make the tedious job slightly less tedious.

  1 件のコメント

Scott Webster
Scott Webster 2015 年 2 月 19 日
If I'm understanding what you are trying to do correctly, you might want to considering using alternative tools to get at the data, several of which exist, e.g.

Sign in to comment.

採用された回答

Knut
Knut 2013 年 3 月 26 日
編集済み: Knut 2013 年 3 月 26 日
Here is my suggested solution. Nothing ground-breaking, but a bit fiddly for my skills using axes.
%%generate some trivial data
[b1,a1] = butter(2,1200./48e3);
[b2,a2] = butter(2,1200./48e3,'high');
H1 = freqz(b1,a1,512,48e3);
H2 = freqz(b2,a2,512,48e3);
im = imread('ngc6543a.jpg');
%%do the actual plotting
figure
%define plot extent so that image can be aligned with plot
xrng = [20 30e3]./1000;
yrng = [-60 10];
image(xrng,yrng,im);
ax1 = gca;
%get rid of pixel ticklabels
set(ax1,'YTickLabel', [], 'XTickLabel', [])
%color=none to make the image visible
ax2 = axes('Position',get(ax1,'Position'),'Color','none','XScale', 'log');
ylim(yrng)
xlim(xrng)
xlabel('Frequency - kHz')
ylabel('power - dB')
title('Frequency response')
line(W, 20*log10(abs([H1 H2])),'Parent',ax2);
legend('lopass', 'hipass')
Inspired by:

  2 件のコメント

Stanley Kubrick
Stanley Kubrick 2015 年 2 月 19 日
I've actually just resorted to taking screenshots and overlaying it manually like this:
Star Strider
Star Strider 2015 年 2 月 19 日
@Stanley Kubrick — You should probably post that also as a Comment to your post Semilog plot with background image.

Sign in to comment.

その他の回答 (0 件)


Translated by