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صورة:Waveforms.png


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 New SVG image

This shows several waveforms: sine wave, square wave, triangle wave, and rising sawtooth wave.

I think it's good to show them next to each other for context.

The fundamentals of each have the same frequency and phase.

Instructions

See Wikipedia graph-making tips.

Generated in gnuplot with the following script (save as waveforms.plt and then open in gnuplot):

set samples 9001 set terminal postscript enhanced landscape color solid lw 2 "Times-Roman" 20 set output "waveforms.ps" # Define the four curves sine(x) = sin(x*pi) #(Originally was going to graph others as functions, but data files are easier and more accurate) # Set up a four-pane multiplot set size 1,1 set origin 1,0 set multiplot set grid # Set range of x axis set xrange [0:6] # Gridlines at every cycle set ytics 1 # Ticks distract from wave shapes set ticscale 0 # Show extents but don't waste space set yrange [-1.5:1.5] # No numbers needed; these are for shape comparison set format x "" set format y "" set nokey # Squish them together slightly # (Doesn't accept fractional margins???) set bmargin 1 set tmargin 0 # Plot each graph # I don't understand how the labels work in multiplot, but this gives the right output set size 1,0.25 set origin 0,0.75 set label 1 "Sine" at 5.5, 0.5 c plot sine(x) 1 set size 1,0.25 set origin 0,0.5 set label 1 "Square" at 5.5, 0.5 c plot "square.dat" with lines 2 set size 1,0.25 set origin 0,0.25 set label 1 "Triangle" at 5.5, 0.5 c plot "triangle.dat" with lines 3 set size 1,0.25 set origin 0,0 set label 1 "Sawtooth" at 5.5, 0.5 c plot "sawtooth.dat" with lines 4

and data files:

square.dat

# XY1 0 1 1 1 1 -1 2 -1 2 1 3 1 3 -1 4 -1 4 1 5 1 5 -1 6 -1

triangle.dat

# XY1 0 0 0.5 1 1.5 -1 2.5 1 3.5 -1 4.5 1 5.5 -1 6 0

sawtooth.dat

# XY1 0 0 1 1 1 -1 3 1 3 -1 5 1 5 -1 7 1

Then I opened the waveforms.ps file in a text editor to edit the line colors and linestyles, as per this description. This avoids needing to open in proprietary software, and really isn't that difficult (especially if you don't know the commands in the proprietary software either).  ;-) Identify the lines easily by their color (the arrow is currently magenta and I want it to be black. Ah, there is the entry with 1 0 1, red + blue = magenta) or by using the gnuplot linestyle−1. (For instance, gnuplot's linestyle 3 corresponds to the ps file's /LT2.) Then you can edit the colors and dashes by hand.

I changed the original:

/LT1 { PL [4 dl 2 dl] 0 1 0 DL } def

into this:

/LT1 { PL [4 dl 2 dl] 0 0.7 0 DL } def

to make the green a little less neon.

To convert the PostScript file to PNG:

  1. Open it in the GIMP (make sure you have ghostscript installed! - Windows instructions)
    • Enter 500 under Resolution (it doesn't say "DPI" but I think that's what it means)
    • Uncheck Try bounding box (since the bounding box cuts off the edge, unfortunately. You can try with the bounding box first.)
    • Enter large values for Width and Height
    • Check Color
    • Check Strong anti-aliasing for both graphics and text
  2. Crop off extra whitespace (Shift+C if you can't find it in the toolbox)
  3. Possibly need to rotate it: Click Image → Transform → Rotate 90 degrees clockwise
  4. Filters → Blur → Gaussian blur at 2.0 px (No need to blur if you use strong anti-aliasing during conversion. I see no significant difference between end results.)
  5. Image → Scale Image...
    • Width and Height at 25%
    • Cubic interpolation
  6. You can view at normal size if you want by pressing 1, Ctrl+E
  7. Save as Waveforms.png

Created by User:Omegatron using gnuplot, possibly with post-processing in the GIMP (PNG) or Inkscape (SVG)


I, the copyright holder of this work, hereby publish it under the following licenses:
Some rights reserved
Creative Commons Attribution iconCreative Commons Share Alike icon		 This file is licensed under the Creative Commons Attribution ShareAlike license versions 3.0, 2.5, 2.0, and 1.0

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GNU head Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation license, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation license".

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