[Arjen Markus] (13 january 2009) At the moment I am involved in a project where I frequently need to edit timeseries in an input file.
For instance: to multiply the wind velocity with a factor 0.8 to see what the effect is on the result of my computations. A tedious
task if done by hand. Many people would probably use a spreadsheet for this task: copy the raw data into the spreadsheet, put a
formula like "=0.8*$A1" in cell B1, copy that to the cells below, and export the results to the input file.

That is all very well, but to me that is rather laborious - I am lousy with spreadsheets, I get confused easily and I find them
rather tedious to use (lots of mouse clicks for instance). 

One of the nice features of Tcl, in my opinion, is the very limited restrictions it poses on a program. So, when I have
a timeseries of this form for instance:

======
2008/07/05-03:00:00 3.266219192649675
2008/07/06-03:00:00 5.680730549305496
2008/07/07-03:00:00 8.375445823799266
2008/07/08-03:00:00 6.92001047014345
2008/07/09-03:00:00 4.2700598446601665
2008/07/10-03:00:00 4.939019208757603
2008/07/11-03:00:00 5.869121431091313
2008/07/12-03:00:00 5.400178789428884
2008/07/13-03:00:00 2.49166379101902
2008/07/14-03:00:00 4.607648466722291
2008/07/15-03:00:00 5.109895484028547
...
======

then I can just surround it with { } to get a valid list:

======
set data {
2008/07/05-03:00:00 3.266219192649675
2008/07/06-03:00:00 5.680730549305496
2008/07/07-03:00:00 8.375445823799266
2008/07/08-03:00:00 6.92001047014345
2008/07/09-03:00:00 4.2700598446601665
2008/07/10-03:00:00 4.939019208757603
2008/07/11-03:00:00 5.869121431091313
2008/07/12-03:00:00 5.400178789428884
2008/07/13-03:00:00 2.49166379101902
2008/07/14-03:00:00 4.607648466722291
2008/07/15-03:00:00 5.109895484028547
...
}
======

Then, add a loop like this after the data:

======

foreach {time velocity} $data {
    puts "$time [expr {0.8*$velocity}]"
}

======

and run the program - the output is a timeseries with the velocity scaled to 80% of its 
original value. I can plug that output directly into the input file.

If I need a bit more sophisticated processing and even a picture to get a better feeling
for the data, well, no problem:

======

#
# Get rid of the first column - no need for it now
#
set velocity {}
foreach {time vel} $data {
    lappend velocity $vel
}

package require math::statistics
package require Plotchart

pack [canvas .c -width 400 -height 300]
set p [::Plotchart::createXYPlot .c {0 50 10} {0 1 0.1}]

set i 0
foreach value [::math::statistics::autocorr $velocity] {
    puts "$i $value"
    $p plot data $i $value
    incr i
}

======

and the result is a picture of the autocorrelation function of the data. I would not 
know a (fast) way of squeezing that out of a spreadsheet. But of course, I am no
expert wrt spreadsheets.


----
[newp] (13 january 2009) The above example throws an error in the Plotchart::create command:

invalid command name "console"

[LV] newp, are you trying the example on Windows? If so, then I expect the issue is that you are using a console only version of the tclsh interpreter, or at the very least you need to do a 

package require Tk

before you try the example.  If you are not using Windows, then one of those packages has a bug in that they are trying to use a Tk command ([console]) which unfortunately doesn't exist on your platform.

On SPARC Solaris , using Tcl 8.5, the above doesn't generate an error about console. However, the data graphed along the Y axis is a bit peculiar. I copied the above data setting, leaving out the "...". I see numbering along the y axis of 0.0, 0.1, 0.2, 00000000004 (the left side of the number is clipped), 0.4, 0.5, 0.6, 0.7, 99999999999, 99999999999, 99999999999 (again, the left side of the numbers are clipped).


----
[newp] (13 january 2009) You are right: I am on Windows XP (with Tcl version at 8.4.17) and I tried it with Tkcon.  Even when I added the "package req Tk" part, I get the error.  But when I do it from a wish console, all is OK.


The graph does look a bit peculiar.  Perhaps it is because of the data range?



----
!!!!!!
%| [Category Application] |%
!!!!!!