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function y = var(x,w,dim)
// This function var estimate the variance of the values in X.
// Calling Sequence
// y=var(x)
// y=var(x,w)
// y=var(x,w,dim)
// Parameters
// x: a vector or matrix.
// w: weight vector W of length X, or may take the value of 0 and 1. The default value is 0. Consider only non-negative values.
// dim: consider the variance along the dimension of X. 1 for clumun wise variamce and 2 for row wise variance.
// y: returns the variance of the values in X.
// Examples
// x=[1.2, 5, 10, -20, 12,10,5,20,32,20];
// w=1:10;
// dim=2;
// y=var(x, w, dim) ;
// See also
// Authors
// Jitendra Singh
if argn(2)==1 then
if type(x)==10 then
x=ascii(x)
end
if size(x,1)==1 |size(x,2)==1 then
sd=stdev(x)
else
sd=stdev(x,1)
end
y=sd.^2;
end
if argn(2)<=3 & argn(2)>1 then
if size(x,1)==1 |size(x,2)==1 then
sd=stdev(x);
n=length(x);
y1= sd.^2;
if length(w)==1 & w==0 then
y=y1;
elseif length(w)==1 & w==1 then
y=y1*((n-1)/n);
elseif length(w)==n & and(w>=0) then
if size(x,1)~=size(w,1) then
w=w';
end
wmean=sum(x.*w)/sum(w);
x1=(x-wmean).^2;
l=length(find(w>0));
sd=((sum(w.*x1))/(((l-1)/l)*sum(w)));
y=(sd)*((n-1)/n);
elseif length(w)~=size(x)& length(w)>1 then
error ('The length of W must be compatible with X.')
else
error('W must be a vector of nonnegative weights, or a scalar 0 or 1.')
end
else
n=size(x,1)
sd=stdev(x,1)
y1=sd.^2;
if length(w)==1 & w==0 then
y=y1;
elseif length(w)==1 & w==1 then
y=y1*((n-1)/n);
elseif length(w)==n & and(w>=0) then
for i=1:size(x,2)
xx=(x(:,i))
if size(xx,1)~=size(w,1) then
w=w';
end
wmean=sum(xx.*w)/sum(w);
x1=(x(:,i)-wmean).^2;
l=length(find(w>0));
sd(i)=sum((w.*x1)/(((l-1)/l)*sum(w)));
end
y=sd*((l-1)/l);
elseif length(w)~=size(x,1) & length(w)>1 then
error ('The length of W must be compatible with X.')
else
error('W must be a vector of nonnegative weights, or a scalar 0 or 1.')
end
end
end
if argn(2)==3 then
if dim==2 then
if size(x,1)==1 | size(x,2)==1 then
if size(x,1)==1 then
y=y;
elseif size(x,2)==1 & length(w)== length(x) then
error ('The length of W must be compatible with X.')
else
y=zeros(size(x,1),size(x,2))
end
else
n=size(x,2)
sd=stdev(x,2)
y1=sd.^2;
if length(w)==1 & w==0 then
y=y1;
elseif length(w)==1 & w==1 then
y=y1*((n-1)/n);
elseif length(w)==n & and(w>=0) then
for i=1:size(x,1)
xx=(x(:,i))
if size(xx,1)~=size(w,1) then
w=w';
end
wmean=sum(xx.*w)/sum(w);
x1=(x(:,i)-wmean).^2;
l=length(find(w>0));
sd(i)=sum((w.*x1)/(((l-1)/l)*sum(w)));
end
y=sd*((l-1)/l);
else
error('The length of W must be compatible with X.')
end
end
end
if dim==1 then
if size(x,1)==1 | size(x,2)==1 then
if size(x,2)==1 then
y=y;
elseif size(x,1)==1 & length(w)== length(x) then
error ('The length of W must be compatible with X.')
else
y=zeros(size(x,1),size(x,2))
end
end
end
if dim>2 then
if length(w)==1 & w==1 | w==0 then
y=zeros(size(x,1), size(x,2))
else
error ('The length of W must be compatible with X.')
end
end
if dim<=0 then
error('Dimension argument must be a positive integer scalar within indexing range.')
end
end
endfunction
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