Category : Pascal Source Code
Archive   : ENGR.ZIP
Filename : CFIT1A.PAS

program cfit1A; { -> 142 }
{ Pascal program to perform a linear least-squares fit }

const max = 20;

type index = 1..max;
ary = array[index] of real;

var x,y,y_calc : ary;
n : integer;
first,done : boolean;
seed,a,b : real;

external procedure cls;

function random(dummy: integer): real;
{ random number 0-1 }
{ define seed=4.0 as global }

const pi = 3.14159;

var x : real;
i : integer;

begin { RANDOM }
x:=seed+pi;
x:=exp(5.0*ln(x));
seed:=x-trunc(x);
random:=seed
end; { RANDOM }



procedure get_data(var x,y: ary;
var n: integer);
{ get values for n and arrays x,y }
{ y is randomly scattered about a straight line }

const a = 2.0;
b = 5.0;

var i,j : integer;
fudge : real;

begin
write('Fudge? ');
readln(fudge);
if fudge<0.0 then done:=true
else
begin
repeat
write('How many points? ');
readln(n)
until (n>2) and (n<=max);
if first then first:=false else cls;
for i:=1 to n do
begin
j:=n+1-i;
x[i]:=j;
y[i]:=(a+b*j)*(1.0+(2.0*random(0)-1.0)*fudge)
end { for-loop }
end { if }
end; { procedure get_data }


procedure write_data;
{ print out the answers }
var i : integer;

begin
writeln;
writeln(' I X Y');
for i:=1 to n do
writeln(i:3,x[i]:8:1,y[i]:9:2);
writeln
end; { write_data }

begin { MAIN program }
cls;
seed:=4.0;
first:=true;
done:=false;
repeat
get_data(x,y,n);
if not done then
begin
write_data;
{ ***** ---> more lines to be added here ********* }
end
until done
end.