Taking the modulo of column data

[Gert]

When trying to take the modulo of a column variable, I get:

"script_name", line 5: can only mod ints

Line 5 refers to:

plot "<data_file_name>" using
<column_number_1>:($<column_number_2>%<mod_base>) title '<title>' with
lines

The data of <column_number_2> does indeed solely consist of integers.

So, is this is a bug? Or do I have to provide some sort of casting to tell
gnuplot the data are integers.

Thank you,

Gert

[Hans-Bernhard Broeker]

Gert <Eagerb...@hotmail.com> wrote:

> The data of <column_number_2> does indeed solely consist of integers.

You may know that, but gnuplot doesn't. You have to tell it, by
casting, like this:

plot 'datafile' using 1:(int($2) % 2)

--
Hans-Bernhard Broeker (bro...@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

[Gert]

> > The data of <column_number_2> does indeed solely consist of integers.
>
> You may know that, but gnuplot doesn't. You have to tell it, by
> casting, like this:
>
> plot 'datafile' using 1:(int($2) % 2)

Thank you very much. I had looked into many online tutorials, but still
hadn't find any information about this casting.

Did I overlook the existence of a decent tutorial which does incorporate
these kind of manipulations (...and much more)?

Gert

[Hans-Bernhard Broeker]

Gert <Eagerb...@hotmail.com> wrote:

> Did I overlook the existence of a decent tutorial which does incorporate
> these kind of manipulations (...and much more)?

I don't think so. You did overlook the actual gnuplot documentation,
though. To be more precise: "help expression", which says:

Note that gnuplot uses both "real" and "integer" arithmetic, like FORTRAN and
C. Integers are entered as "1", "-10", etc; reals as "1.0", "-10.0", "1e1",
3.5e-1, etc. The most important difference between the two forms is in
division: division of integers truncates: 5/2 = 2; division of reals does
not: 5.0/2.0 = 2.5. In mixed expressions, integers are "promoted" to reals
before evaluation: 5/2e0 = 2.5. The result of division of a negative integer
by a positive one may vary among compilers. Try a test like "print -5/2" to
determine if your system chooses -2 or -3 as the answer.

This explains why the problem occurs in the first place.

[Gert]

> I don't think so. You did overlook the actual gnuplot documentation,
> though. To be more precise: "help expression", which says:
>
> Note that gnuplot uses both "real" and "integer" arithmetic, like FORTRAN and
> C. Integers are entered as "1", "-10", etc; reals as "1.0", "-10.0", "1e1",
> 3.5e-1, etc. The most important difference between the two forms is in
> division: division of integers truncates: 5/2 = 2; division of reals does
> not: 5.0/2.0 = 2.5. In mixed expressions, integers are "promoted" to reals
> before evaluation: 5/2e0 = 2.5. The result of division of a negative integer
> by a positive one may vary among compilers. Try a test like "print -5/2" to
> determine if your system chooses -2 or -3 as the answer.
>
> This explains why the problem occurs in the first place.

Well, actually, I did read this part of the documentation. So I understood
the nature of the problem. But the documentation didn't mention anything
about the possibility to perform casting.

Thanks anyway for pointing me out.

Greetings,

Gert

[galax...@gmail.com]

This does not work in you use:

set datafile separator ","

for comma separated data (CSV)

This must be a bug right?

[galax...@gmail.com]

"if" you use: