I just released a GSL For Delphi Header translation at github .
GSL For Delphi is a delphi header translation of GNU Scientific Library at https://www.gnu.org/software/gsl/ , lastest support version is 2.5+. Prebuilt windows dll also included in the bin folder.
procedure TFormMain.btnStatClick(Sender: TObject);
var
I: Integer;
X,Y:array [0..3] of Double;
c0,c1, cov00, cov01, cov11, sumsq:double;
begin
for I := 0 to 3 do
begin
X[I]:=I;
Y[I]:=I*1.23+3.64;
end;
gsl_fit_linear(@X[0], 1, @Y[0], 1, 4, @c0,@c1,@cov00, @cov01, @cov11, @sumsq );
end;