# how to plot the data over an image of graph to validate the data?

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DGM
on 25 May 2024

### Accepted Answer

DGM
on 25 May 2024

Edited: DGM
on 25 May 2024

You can plot things over an image, but good luck guessing whether or not your image features actually line up with the coordinate space or if they're off by half a line width.

inpict = imread('2122511.png');

% box coordinates in px

r = [43.51 15.51 214.98 153.98];

% box coordinates in data

xrange = [0 4.5];

yrange = [-0.2 0.4];

% crop the image

inpict = imcrop(inpict,r);

% flip the image

inpict = flipud(inpict);

% display the image

image(inpict,'xdata',xrange,'ydata',yrange)

set(gca,'ydir','normal')

hold on

% plot something over it

load fakedata

plot(xfn,yfn,'*');

Why make a blurry, questionably-aligned stack of objects when you can do this? It's still an estimation, but it's clean, and you can be as deliberate as you want in making sure the transcription matches the image.

% using the following FEX tools:

% https://www.mathworks.com/matlabcentral/fileexchange/72225-load-svg-into-your-matlab-code

% filename of manually-fit svg file

fname = '2122511.svg.fakeextension.txt';

% data range from original image axis labels

% this is where the rectangle is drawn in the SVG

xrange = [0 4.5];

yrange = [-0.2 0.4];

% spline discretization parameter [0 1]

coarseness = 0.01;

% get plot box geometry

str = fileread(fname);

str = regexp(str,'((?<=<rect)(.*?)(?=\/>))','match');

pbx = regexp(str,'((?<=x=")(.*?)(?="))','match');

pby = regexp(str,'((?<=y=")(.*?)(?="))','match');

pbw = regexp(str,'((?<=width=")(.*?)(?="))','match');

pbh = regexp(str,'((?<=height=")(.*?)(?="))','match');

pbrect = [str2double(pbx{1}{1}) str2double(pby{1}{1}) ...

str2double(pbw{1}{1}) str2double(pbh{1}{1})];

% get coordinates representing the curve

S = loadsvg(fname,coarseness,false);

% if there are multiple paths you want to extract

% you'll need to do do the rescaling, etc for each element of S

for k = 1:numel(S) % there are multiple curves

x = S{k}(:,1);

y = S{k}(:,2);

% rescale to fit data range

x = xrange(1) + diff(xrange)*(x-pbrect(1))/pbrect(3);

y = yrange(1) + diff(yrange)*(pbrect(4) - (y-pbrect(2)))/pbrect(4);

% get rid of nonunique points

% this may or may not be needed depending on the shape

% of the curves and how they're to be processed

[x,idx,~] = unique(x,'stable');

y = y(idx);

% shove the prepared data back into S for later

S{k} = [x y];

end

% plot

for k = 1:numel(S)

x = S{k}(:,1);

y = S{k}(:,2);

plot(x,y); hold on

end

grid on;

xlim(xrange)

ylim(yrange)

% plot something over it

load fakedata

plot(xfn,yfn,'.');

Yeah, but where exactly do those cuves lie on the original image?

They line up exactly where I chose to put them.

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