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Call: FIT_GAUSSIAN


reference

The histogram is referenced via a global variable that has usually been returned by a call to BOOK_HISTOGRAM or to GET_HISTOGRAM. This argument may also be an expression that results in a histogram.

The argument is not modified on return.


x

A 1-dimensional vector that contains the abscissa of the points on which the fit is to be performed.

This vector should have the same size as y.


y

A 1-dimensional vector that contains the function values of the points on which the fit is to be performed.

This vector should have the same size as x.


err_y

Either a scalar which is interpreted as a common error on all function values (y) or a 1-dimensional vector of the same length as x and y and which contains for each point the error in the function value.

integral

The contents of the fitted Gaussian.

There is no need to initialise this argument - the initial value for the fitting procedure is set to the sum of the histogram or Y array.

This argument must be modifiable, i.e. it can not be a constant nor an expression.


mean

The central value of the fitted Gaussian.

There is no need to initialise this argument - the initial value for the fitting procedure is set to the mean of the histogram or arrays.

This argument must be modifiable, i.e. it can not be a constant nor an expression.


sigma

The standard deviation of the fitted Gaussian.

There is no need to initialise this argument - the initial value for the fitting procedure is set to the RMS of the histogram or arrays.

This argument must be modifiable, i.e. it can not be a constant nor an expression.


errors

The errors returned are the square roots of the diagonal elements of the covariance matrix, multiplied by a correction factor equal to:

     sqrt(chi**2/(#points - #parameters))

This correction factor is equal to 1 if the errors to the data points have been assigned correctly.

Errors are only returned upon request. The corresponding arguments must be modifiable, that is, they can neither be constants nor expressions.


options

The options string may contain the keywords listed in the table below. The keywords should be separated by blanks or commas. Additional text may be added - no error message will be issued if unrecognised keywords are used.

Option Meaning Defaults
EQUAL Assume equal weight of all points Not default
NOPLOT Don't plot the histogram and fit Default
NOPRINT Don't print details during the fit Default
PLOT Plot the histogram with fit Not default
POISSON Assume Poisson errors Default
PRINT Print details during the fit Not default


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Formatted on 0100-09-02 at 06:56.