File AMVAC.ZIP from The Programmer’s Corner in
Category Science and Education
Fit a user defined curve to a set of data.
File Name File Size Zip Size Zip Type
AMVAC.DAT 1182 585 deflated
AMVAC.DOC 2809 1270 deflated
AMVAC.EXE 72847 40618 deflated

## Contents of the AMVAC.DOC file

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.sp 1
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Gentle User,

AMVAC is a program that allows you to fit a curve to a set of data
points defining a dependent variable that is a linear combination of
nonlinear functions of one or more independent variables. For example,
say you have 4 variables: 1 dependent variable (X1) and 3 independent
variables (X2,X3,X4). An example of such a curve-fit would be the
following:

X3=C1+C2*X2+C3*EXP(X3)+C4*X4*SIN(3.*X4)+C5*COS(X2)+C6*SQRT(X4)

In FORTRAN this function might be written:

FUNCTION X1(X2,X3,X4)
DATA C1,C2,C3,C4,C5,C6/1.,2.,3.,4.,5.,6./
X1=C1
&+C2*X2
&+C3*EXP(X3)
&+C4*X4*SIN(3.*X4)
&+C5*COS(X2)
&+C6*SQRT(X4)
RETURN
END

AMVAC will pick the functions for you (select: automatic) or let you
pick them (select: manual).

To run AMVAC just enter "AMVAC" (without the quotes). It's all
interactive. AMVAC can read data in free-format from a file (up to 9
columns of data or 128 characters per line whichever is smaller). You
can also enter the data from the keyboard.

You can edit the data. That is, list it and change values. Then when
you have verified it, AMVAC will ask you if you want automatic selection
of functions. You can try this and see what you get. It really should
be sort of self-explanatory.

You can see the form of the curve-fit by responding "Y" (without the
quotes) when asked. What AMVAC will list is the actual FORTRAN code,
just like you would put into a program to use the curve-fit. It may
look a little strange, but it will work just fine.

You can check to see how the curve-fit does by responding "Y" (without
the quotes) when asked to check agreement.

You can evaluate the curve-fit at as many locations as you want (just
enter a blank line or "NO" to quit evaluating).

You can perform several curve-fits on the same data without entering it
again. Just wait until the end and it will ask you "another fit on the
same data?(Y/N)."

To run the example that is included give AMVAC the file name "AMVAC.DAT"
and tell it to read 9 columns of data. Then try automatic correlation
of X2 as a function of X1. Then try automatic correlation of X2 as a
function of X3-X9.

P.S. AMVAC will work even without a math coprocessor; but I doubt that
you will have the patience for it to get through a single case.

Dudley J. Benton
TVA Engineering Lab
P.O. Drawer E
Norris, TN 37828
615-632-1887

December 18, 2017