# Image of ideal particle

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engineerOfPhysics on 11 Aug 2013
Hello matlab community.
I am working on a project, the first part of the project that ı need to understand basic idea of the code below. Can anybody explain ?
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function h=simage(img,numcolor,axistype,minimg,maximg);
imscale=0; if ~exist('axistype')
axistype=['image'];
end
if ~exist('minimg') & ~exist('maximg')
imscale=1;
else
if (~exist('maximg'))
maximg=max(img(:));
end
if (~exist('minimg'))
minimg=min(img(:));
end
if (maximg==0 & minimg==0)
minimg=min(img(:));
maximg=max(img(:));
end
end
if ~exist('numcolor') numcolor=64; end
if imscale==0 h=imagesc(img,[minimg maximg]); else h=imagesc(img); end
axis(axistype);
end
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if you run the code shown below with the first one together , you will see the some figure like a particle. ---------------------------------------
function ipi=ipf(cr,D,w)
ipi=(1-tanh((abs(cr)-D/2)/w))/2;
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For example I do not understand the meaning of exist in the first code. What is it used for ?
I do not have a much time, I look at some matlab books but I can not find anything about the situation. Please help..
Thank you..

dpb on 11 Aug 2013
Edited: dpb on 11 Aug 2013
...For example I do not understand the meaning of exist in the first code. What is it used for ?
I do not have a much time, I look at some matlab books but I can not find anything about the situation.
Well, it would undoubtedly take far less of your valuable time (and be much less annoying(*) here as well) if you were to simply type
doc exist
at the command line first.
(*) Or, if you're going to ask at least don't whine while doing so...
engineerOfPhysics on 11 Aug 2013
I get the particle image using the code
D=12; %diameter
w=1.3; %width
ss=2*fix(D/2+4*w/2)-1;
os=(ss-1)/2;
[xx yy]=ndgrid(-os:os,-os:os); %ideal particle image grid
h=figure(1);
set(h,'posisiton',[100 100 400 400],'color','w');
simage(ipf(r,D,w));
If you use code with two codes up ı wrote, you can see the particle. Yeah as you say numcolor is not used. I remove it from the code, I get exactly same result.
Thanks... I will spend your time in the next again :)