Calculate the minimum and maximum data with 'Gnuplot'

D.GH

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May 20, 2008, 4:04:57 PM5/20/08

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Hello,

I would like if is possible to calculate the maximum and minimum from
a data file.

My data in the following file (MyData.dat)

22.871536
22.029848
18.641526
11.097671
10.769791
14.375998
9.353067
16.888065
10.120260
11.920241
14.518588
26.042677
9.516011
16.486201
23.851848
10.483301

I do not know neither the maximum nor the maximum.
If I could calculate them with 'Gnuplot', it will help me with the
following code:
#############################
Min= .......
Max= .......
NumberBin=10
Shift=(Max-Min)/NumberBin
bin(x) = Min + Shift * int((x - Min) / Shift)
set style fill solid .2 border -8
plot 'MyData.dat' u (bin($1)):(1.0) title '' smooth frequency with
boxes
set term postscript eps color
set out 'Myfig.eps'
set size 0.7, 0.7
replot
#############################

Thank you for your ideas

Dariush

Oliver Jennrich

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May 20, 2008, 5:07:54 PM5/20/08

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"D.GH" <dariush.gh...@gmail.com> writes:

> Hello,
>
> I would like if is possible to calculate the maximum and minimum from
> a data file.

Yes. But the solution is far from ideal - gnuplot is a plotting tool,
not a data processing tool.

Anyway - you want to run once through the data and find the maximum
and the minimum:

------8<------8<------8<------8<------8<------8<-------
# Define two helper functions
ismin(x) = (x<min)?min=x:0
ismax(x) = (x>max)?max=x:0

# Initialise the 'global' vars
max=-1e38
min=1e38

# Run through the data and pass it to the helper functions.
# Any expression for the 'using' will do, as long as it contains both
# helper functions
plot "MyData.dat" u 0:(ismin($0)*ismax($0))

# Now, max and min will hold the maximum and minimum of column 0 of
# your data

print max
print min
------8<------8<------8<------8<------8<------8<-------

A different solution would require a working perl installation:

max=`! perl -e '$max=-1e38; while (<>) {@t=split; $max=$t[0] if $t[0]>$max}; print $max' < MyData.dat`

--
Space - The final frontier

nicola...@googlemail.com

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May 21, 2008, 2:33:23 AM5/21/08

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An other possibility imho would be to fit the data and calculate the
values from the derivative.

regards

Nicolas

goo...@catking.net

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May 21, 2008, 1:41:37 PM5/21/08

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> > Thank you for your ideas
>
> > Dariush

cleaning Oliver's answer , less work:

grab(x)=(x<min)?min=x:(x>max)?max=x:0;
plot 'datafile.dat' using 1:(grab($1))

you will need gnuplot 4.3 or cvs , this feature is relatively new.

D.GH

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May 21, 2008, 3:12:48 PM5/21/08

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On 20 mai, 23:07, Oliver Jennrich <oliver.jennr...@gmx.net> wrote:

Hello,

Thank you for your proposal, it does not work with me.
I have the following error message :

gnuplot> ismin(x) = (x<min)? min=x:0
^
"Test.gnu", line 2: expecting ':'

Thank you

Dariush

D.GH

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May 21, 2008, 3:30:37 PM5/21/08

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I have the following error message :

gnuplot> grab(x)=(x<min)?min=x:(x>max)?max=x:0;
^
"test4.gnu", line 1: expecting ':'

Dariush

goo...@catking.net

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May 22, 2008, 9:15:24 AM5/22/08

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On May 21, 9:30 pm, "D.GH" <dariush.ghorbanza...@gmail.com> wrote:

> > you will need gnuplot 4.3 or cvs , this feature is relatively new.
>
> I have the following error message :
>
> gnuplot> grab(x)=(x<min)?min=x:(x>max)?max=x:0;
> ^
> "test4.gnu", line 1: expecting ':'
>
> Dariush

what gnuplot version are you using?

D.GH

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May 22, 2008, 4:11:33 PM5/22/08

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gnuplot version 4.2.3 -- binary distribution for MS-Windows 32bit

D.GH

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May 25, 2008, 7:09:38 AM5/25/08

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On 21 mai, 19:41, goog...@catking.net wrote:

Thank you

The code works with 'gnuplot 4.3.'

wenx...@gmail.com

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Oct 12, 2018, 4:39:13 AM10/12/18

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在 2008年5月20日星期二 UTC+2下午10:04:57，D.GH写道：

Chris Elvidge

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Oct 12, 2018, 6:38:06 AM10/12/18

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Use "stats" on datafile to get max and min values

--

Chris Elvidge, England