Simple data plotting example
Arjen Markus (19 july 2002) I have wanted something like this for a long time: a simple little program that can plot the data from a simple file. This is my solution:
- Use emu_graph by Steve Casssidy [L1 ] to do the hard work
- Use a set of simple routines to read the file in question (make that customisable!)
- Put it together in a small script that takes care of the more general tasks.
Note: If the script file "custom.tcl" is present in the working directory, then this will be sourced, for instance to replace the general but simple procs, readNames and readData.
Note: The user-interface is not very pretty, it is effective though.
Sample data file:
time temp rain wind vaporp 1 46 1 27 73 2 41 3 32 71 3 42 0 31 72 4 39 0 32 71 5 37 0 39 66 6 35 1 44 66 7 33 3 42 67 8 33 1 43 67 9 32 2 43 68 10 35 1 41 66 11 27 11 31 65 12 22 9 25 63 13 19 1 24 61 14 15 0 28 61 15 16 1 22 60 16 19 0 26 56 17 16 0 49 46 18 10 0 49 40 19 10 0 51 37 20 4 0 43 39 21 3 0 40 37
The script:
# simplegraph.tcl --
# Script to read and display timeseries
#
# Notes:
# This script defines a number of procs that can be overridden
# via a customised script file in the working directory:
# - openFile - to open a file and prepare for reading
# - readNames - to read the names of the series
# - readData - to read the data for the series
# This is done specifically to make it possible to read (almost)
# any file without touching the script itself.
# The script file should be called "custom.tcl"
# The main script defines default procs that should be effective
# for simple cases.
# openFile --
# Open the file and start looking for data
#
# Arguments:
# filename Name of the file to read
#
# Result:
# infile Handle to the opened file
#
# Side effects:
# A file in question is opened. Lines containing a * or # as
# the first non-blank character are considered comments. The
# first line without this is considered to be a line with the
# names of the columns.
#
proc openFile {filename} {
set infile [open $filename "r"]
return $infile
}
# readNames --
# Read the names of the columns
#
# Arguments:
# infile Handle to the file
#
# Result:
# names List of names, the number indicates the number of
# columns
#
proc readNames {infile} {
#
# Skip the header - if any
#
set pos 0
while { [gets $infile line] >= 0 } {
if { [regexp {[ \t]*[*#]} $line] } {
incr pos
} else {
break
}
}
seek $infile 0 start
while { $pos > 0 } {
gets $infile line
incr pos -1
}
#
# Read the line with the column names
#
gets $infile line
# Force the line to be interpreted as a list
set nocols [llength $line]
return $line
}
# readData --
# Read the data per line
#
# Arguments:
# infile Handle to the file
#
# Result:
# values List of values, representing each column.
# A list of length zero indicates the end of file
#
proc readData {infile} {
while { [gets $infile values] == 0 } { ;# Just go on - skip empty lines }
set nocols [llength $values]
return $values
}
# readFile --
# Read the file and store the data in a (global) array
#
# Arguments:
# filename Name of the file
#
# Result:
# None
#
# Side effects:
# Filled array, ready for display
#
proc readFile {filename} {
global data_array
set infile [openFile $filename]
set data_array(names) [readNames $infile]
set i 0
foreach name $data_array(names) {
set data_array($i) {}
incr i
}
while 1 {
set values [readData $infile]
if { [llength $values] > 0 } {
set i 0
foreach value $values {
lappend data_array($i) $value
incr i
}
} else {
break
}
}
}
# makePlotData --
# Make a list useable by emu_graph
#
# Arguments:
# xindex Index of x data
# yindex Index of y data
#
# Result:
# None
#
# Side effects:
# A dataset for emu_graph
#
proc makePlotData {xindex yindex} {
global data_array
set xydata {}
foreach x $data_array($xindex) y $data_array($yindex) {
lappend xydata $x $y
}
plot data xydata -colour black -lines 1 -points 0 -coords $xydata
}
# updatePlot --
# Update the plot data
#
# Arguments:
# name Name of the variable
# op Operation (both ignored)
#
# Result:
# None
#
# Side effects:
# New plot data for the graph
#
proc updatePlot {name op} {
global data_array
set xindex [lsearch $data_array(names) $::xname]
set yindex [lsearch $data_array(names) $::yname]
makePlotData $xindex $yindex
}
# mainWindow --
# Create the main window
#
# Arguments:
# None
#
# Result:
# None
#
# Side effects:
# A toplevel window with a canvas and some buttons
#
proc mainWindow {} {
global data_array
frame .frm
eval tk_optionMenu .frm.x xname $data_array(names)
eval tk_optionMenu .frm.y yname $data_array(names)
set ::xname [lindex $data_array(names) 0]
set ::yname [lindex $data_array(names) 1]
.frm.x configure -width 10
.frm.y configure -width 10
trace add variable ::xname write {after 200 updatePlot}
trace add variable ::yname write {after 200 updatePlot}
pack .frm.x .frm.y -side top
canvas .cnv -width 600 -height 400 -background lightgrey
button .exit -text "Exit" -command "exit"
pack .frm .cnv -side left
pack .exit -side top
emu_graph plot -canvas .cnv -width 400 -height 300
}
# main --
# Main code, controlling the program
#
global data_array
if { [file exists "custom.tcl"] } {
source "custom.tcl"
}
readFile [lindex $::argv 0]
#
# Get emu_graph
#
source "graph.tcl"
mainWindow
makePlotData 0 1KBK Note that there's an example that just scribbles a graph in the canvas: Shuffle a list: graph results. It shows how readily a "quick-and-dirty" plot can be done, even with nothing but Tcl/Tk!