Image of ideal particle

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..

Answer 1

[dpb]

...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...

[Image Analyst]

You can also place the cursor in any function and type F1. Typing control-D will open up the source code (which is usually just a wrapper for a mex file).

[engineerOfPhysics]

I want just some answer. You do not have to give an answer if it is annoying. Sorry.

I spend my time for that. Do not worry about it.

[engineerOfPhysics]

I check the doc exist. Thanks ı forget for a moment. It is so helpfull.

See it is so easy.. to help..

[dpb]

Meanwhile I've wasted my time reading a frivolous question (written with a privileged attitude besides)...

[engineerOfPhysics]

Can I want you to waste your time for my question again :)

Numcolor variable is used for what? I mean when I change the value 64 to another ones image is not changing. What is the mean of that ?

if ~exist('numcolor')

numcolor=64;

 end

[dpb]

Searching for numcolor in what you posted shows it isn't used.

The only references to it are in the argument list and the location where it is defined if non-existent. But, there's no reference to it after that point so it's superfluous. For the answer to why you'll have to ask whoever supplied the function to begin with.

[engineerOfPhysics]

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

r=abs(xx+i*yy); %radial coordinate

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 :)