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Average and others over columns

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Hi

First of all, thank you very much to everyone that contribute/have
contributed to gnuplot for such a great tool. I have been using it for
over 15 year now, and it is still the best tool there is.

Now I think I can contribute something back, if people are interested.
I have been playing with the idea of adding some functions that
produce averages, standard deviations, max, min etc of ranges, ie
something like:

plot 'file.csv' u 1:(average($2:$5))

would plot the average of columns 2 through 5, etc.

Would people be interested in such a feature?

If so, I have got some way into implementing it, though I think I need
some help on how to generate the correct action table. At the moment I
have gone for the average function taking a string argument, and then
parsing the range separately, to avoid having to change how the using
statements are parsed (the ':' would have to be interpreted
differently depending on where it is found and I don't want my change
to be too wide ranging).

I have now two issues:

* the functions that exist at the moment take a fixed number of
arguments (one from what I can see), but I need to pass an array, and
the value struct does not provide for it, so I suggest to add a field
to the v union to contain an array with the values to average over, so
it would look something like:

typedef struct value {
    enum DATA_TYPES type;
    union {
	int int_val;
	struct cmplx cmplx_val;
	char *string_val;
	double *col_values;
    } v;
} t_value;

and the DATA_TYPES enum to look like:

enum DATA_TYPES {
	INTGR=1,
	CMPLX,
	STRING,
	COLUMN_RANGE
};

so that the receiving function can check whether the argument contains
the right data.

is this change reasonable?

* the second problem is where in the code is the actual value of the
column put into a.v.cmplx_val? I can follow the code up to where the
action table for the expression is generated, but I am having trouble
unraveling where I should create the array and feed it into the action
table (I haven't done any complex C programing for a ver long time),
anyone could point me in the right direction?

Best regards

Carlos

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Average and others over columns Carlos <carlosa.rega@gmail.com> - 2011-03-30 09:05 -0700

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