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size(400,200,IgnoreAspect);
import graph;
import stats;
file fin=input("leastsquares.dat").line();
real[][] a=fin.dimension(0,0);
a=transpose(a);
real[] t=a[0], rho=a[1];
// Read in parameters from the keyboard:
//real first=getreal("first");
//real step=getreal("step");
//real last=getreal("last");
real first=100;
real step=50;
real last=700;
// Remove negative or zero values of rho:
t=rho > 0 ? t : null;
rho=rho > 0 ? rho : null;
scale(Log(true),Linear(true));
int n=step > 0 ? ceil((last-first)/step) : 0;
real[] T,xi,dxi;
for(int i=0; i <= n; ++i) {
real first=first+i*step;
real[] logrho=(t >= first & t <= last) ? log(rho) : null;
real[] logt=(t >= first & t <= last) ? -log(t) : null;
if(logt.length < 2) break;
// Fit to the line logt=L.m*logrho+L.b:
linefit L=leastsquares(logt,logrho);
T.push(first);
xi.push(L.m);
dxi.push(L.dm);
}
draw(graph(T,xi),blue);
errorbars(T,xi,dxi,red);
crop();
ylimits(0);
xaxis("$T$",BottomTop,LeftTicks);
yaxis("$\xi$",LeftRight,RightTicks);
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