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This image, as well as the following text, is derived from Image:Butterworth_response.png.

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

 

This plot was created with Gnuplot by n.

Then I opened the ellip.ps file in a text editor to edit the line colors and linestyles, as per this description archive copy at the Wayback Machine. 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:

/LT0 { PL [] 1 0 0 DL } def
/LT1 { PL [4 dl 2 dl] 0 1 0 DL } def
/LT2 { PL [2 dl 3 dl] 0 0 1 DL } def
/LT3 { PL [1 dl 1.5 dl] 1 0 1 DL } def

into this:

/LT0 { PL [] 0 0 1 DL } def
/LT1 { PL [4 dl 2 dl] 0.5 0.5 0.5 DL } def
/LT2 { PL [6 dl 3 dl] 0.3 0.3 1 DL } def
/LT3 { PL [] 0 0 0 DL } def

Then I displayed the ellip.ps using the Mac Preview App, and used SnapNDrag to save the useful part of the image to a file.

Created by Pfalstad from Image:Butterworth_response.png.

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	This licensing tag was added to this file as part of the GFDL licensing update.http://creativecommons.org/licenses/by-sa/3.0/CC BY-SA 3.0Creative Commons Attribution-Share Alike 3.0truetrue

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You are free:

• to share – to copy, distribute and transmit the work
• to remix – to adapt the work

Under the following conditions:

• attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
• share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.

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