#!/usr/X11R6/bin/robot
! This example shows how to use the "functions" fitvalue and fiterror.
! First do a straight line fit to some data.

! Resets
n
RESET

! get the data
TYPE
The title
X axis label
Y axis label
0.0 7 4
9.9 23 3
21 27 4
29 33 3
40 47 4

! plot the data
G

! The straight line fit itself.
CURFIT
polynomial
1 1
end
! Plot the fit
PLOTCUR

! now plot the same function with the intercept found in the previous
! fits replaced with intercept + error on intercept
! The gradient is allowed to float but starts at the result of the
! previous fit
assign a1
fitvalue{1}
assign a2
fiterror{1}
assign a1
a1+a2

assign a3
fitvalue{2}

! Now the second fit
curfit
polynomial
(a1) a2
end

! and plot the results as a dashed line
plotcurd


! Add annotation to the plot
text
Least squares straight line fit
5 52

! some arrows
arrowhollow
arrow
10 7.8 5.0 14.6
text
Best fit
11 7
arrow
0.9 40.6 6.2 20.4
text
Fit with intercept fixed at best value + error on value
0.0 42