# Restricting a set of data by a spherical radius

2 visualizzazioni (ultimi 30 giorni)
jgillis16 il 3 Ago 2015
Modificato: jgillis16 il 10 Ago 2015
I need to restrict column 3 of the attached text file by a spherical radius with a central number of 12.51 that has a radius that extends 0.7333 in every direction.
##### 6 CommentiMostra 4 commenti meno recentiNascondi 4 commenti meno recenti
Walter Roberson il 3 Ago 2015
What do you want to happen for cases that do not match that?
Is "dec" intended to convey "declination", and is "ra" intended to convey "right ascension" (instead of "radius" for example) ?
What formula should be used to test to see if a value is in range?
jgillis16 il 4 Ago 2015
I have some octave code as a reference... but I don't know how to implement it into matlab (but this code should take care of this problem)
function d=angulardist(ra1,dec1,ra2,dec2)
error(mynargchk(4,4,nargin,"struct"));
if common_size(ra1,dec1) && common_size(ra2,dec2)
error("angulardist: input vector dimensions don't match");
endif
if !common_size(ra1,ra2)
d=sind(dec1).*sind(dec2)+cosd(dec1).*cosd(dec2).*cosd(ra1-ra2);
elseif columns(ra1)==1 && rows(ra2)==1
d=sind(dec1)*sind(dec2)+(cosd(dec1)*cosd(dec2)).*cosd(repmat(ra1,1,length(ra2))-repmat(ra2,length(ra1),1));
else
error("angulardist: input vector dimensions don't match");
endif
idx=find(d>1+eps);
d=real(acosd(d));
if ~isempty(idx)
warning("angulardist: irregular angular coordinates");
d(idx)=nan;
endif
endfunction
function out=selectobjectsinfield(in,RA,DEC,fieldDesc,rejectflag)
error(mynargchk(4,5,nargin,"struct"));
if nargin<5
rejectflag=false;
endif
if isscalar(fieldDesc)
circle=true;
else
circle=false; # rectangle
RAwidth=fieldDesc(1);
DECwidth=fieldDesc(2);
endif
ra=[in(:).RA];
dec=[in(:).dec];
if circle==true
angularDist=angulardist(ra,dec,RA,DEC);
if rejectflag
else
endif
else
decDist=angulardist(ra,dec,ra,DEC);
if rejectflag
else
endif
endif
out=in(idx);
endfunction

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### Risposta accettata

Walter Roberson il 4 Ago 2015
function d=angulardist(ra1,dec1,ra2,dec2)
if ~(isscalar(ra1) || isscalar(dec1) || isequal(size(ra1),size(dec1)) &&
~(isscalar(ra2) || isscalar(dec2) || isequal(size(ra2),size(dec2))
error("angulardist: input vector dimensions don't match");
end
if ~(isscalar(ra1) || isscalar(ra2) || isequal(size(ra1),size(ra2))
d = sind(dec1).*sind(dec2)+cosd(dec1).*cosd(dec2).*cosd(ra1-ra2);
elseif size(ra1,2)==1 && size(ra2,1)==1
d = sind(dec1)*sind(dec2)+(cosd(dec1)*cosd(dec2)).*cosd(repmat(ra1,1,length(ra2))-repmat(ra2,length(ra1),1));
else
error("angulardist: input vector dimensions don't match");
end
idx = find(d>1+eps);
d = real(acosd(d));
if ~isempty(idx)
warning("angulardist: irregular angular coordinates");
d(idx)=nan;
end
end
function out = selectobjectsinfield(in,RA,DEC,fieldDesc,rejectflag)
if nargin<5
rejectflag=false;
end
if isscalar(fieldDesc)
circle = true;
else
circle = false; # rectangle
RAwidth = fieldDesc(1);
DECwidth = fieldDesc(2);
end
ra = [in(:).RA];
dec = [in(:).dec];
if circle == true
angularDist = angulardist(ra,dec,RA,DEC);
if rejectflag
else
end
else
decDist = angulardist(ra,dec,ra,DEC);
if rejectflag
else
end
end
out = in(idx);
end
##### 2 CommentiMostra NessunoNascondi Nessuno
jgillis16 il 4 Ago 2015
Thanks! But, I come across an error
"Error: File: angular.m Line: 7 Column: 79
Expression or statement is incorrect--possibly unbalanced (, {, or [."
It's the first set of '&&' that is causing the issue.
Walter Roberson il 4 Ago 2015
Change the first part to
if ~(isscalar(ra1) || isscalar(dec1) || isequal(size(ra1),size(dec1))) &&
~(isscalar(ra2) || isscalar(dec2) || isequal(size(ra2),size(dec2)))
error("angulardist: input vector dimensions don't match");
end
if ~(isscalar(ra1) || isscalar(ra2) || isequal(size(ra1),size(ra2)))

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