How to plot a graph using C

Katie_lin · 04-07-2009, 01:15 PM

Hi.. I am a beginner in C and I work on linux platform. I need to plot a simple X-Y graph. I have the x co-ords and y co-ords saved in two different integer arrays in correspoding order. I basically need to see if I get a straight line or not. Can I please get help with a sample code or any bits that might help? Thanks a lot.

markcole · 04-07-2009, 01:28 PM

If you are just wanting to know if it is a straight line or not (as in a yes or no answer), just ask yourself how you would check that with pen and paper, then implement the same check in code.

**sean** · 04-07-2009, 01:28 PM

Well you can determine characteristics of the line mathematically. If you still want to visibly display the graph, you should look into a graphics library. SDL might be a good choice. (libsdl.org) Then of course you could use | \ / and -'s to display the line!

ulillillia · 04-07-2009, 01:33 PM

An alternative is to write a BMP file. When I wanted to see how the landscape of my 2D game was going to be, I had the program write a BMP file, at 72,000x48,000 pixels and using 1-bit color. Then just open the bitmap image in a standard image-editing program. All you need to know is the BMP file's format (I like making the width a multiple of 4 for simplicity reasons (32 for the 1-bit image)), and how to change the pixel colors accordingly. 24-bit is the easiest to work with.

quzah · 04-07-2009, 02:27 PM

If you're writing your own (not using a library) method of outputting BMP files, I'd suggest going with TGA instead. They're much simpler to figure out. If you're looking for more file types: Wotsit.org

Quzah.

Maz · 04-07-2009, 02:38 PM

And if you just want to visualize the data aquired by a C program, dump values in a file, and use gnuplot to do the plotting. You can even write a script file doing the plotting using C, and launch gnuplot with simple system("") call. (or fork and exec). re-inventing the wheel can be cool and teach you a lot, but if the point is to get results...

04-07-2009, 01:15 PM	#1
Katie_lin Registered User Join Date: Apr 2009 Posts: 1	How to plot a graph using C Hi.. I am a beginner in C and I work on linux platform. I need to plot a simple X-Y graph. I have the x co-ords and y co-ords saved in two different integer arrays in correspoding order. I basically need to see if I get a straight line or not. Can I please get help with a sample code or any bits that might help? Thanks a lot.
Katie_lin is offline

04-07-2009, 01:28 PM	#2
markcole Registered User Join Date: Apr 2007 Posts: 46	If you are just wanting to know if it is a straight line or not (as in a yes or no answer), just ask yourself how you would check that with pen and paper, then implement the same check in code.
markcole is offline

04-07-2009, 01:28 PM	#3
sean Super Moderator Join Date: Sep 2001 Posts: 4,680	Well you can determine characteristics of the line mathematically. If you still want to visibly display the graph, you should look into a graphics library. SDL might be a good choice. (libsdl.org) Then of course you could use \| \ / and -'s to display the line!
sean is offline

04-07-2009, 01:33 PM	#4
ulillillia Math wizard Join Date: Dec 2006 Location: Minot, ND, USA Posts: 516	An alternative is to write a BMP file. When I wanted to see how the landscape of my 2D game was going to be, I had the program write a BMP file, at 72,000x48,000 pixels and using 1-bit color. Then just open the bitmap image in a standard image-editing program. All you need to know is the BMP file's format (I like making the width a multiple of 4 for simplicity reasons (32 for the 1-bit image)), and how to change the pixel colors accordingly. 24-bit is the easiest to work with. __________________ High elevation is the best elevation. The higher, the better the view! My computer: XP Pro SP3, 3.17 GHz C2D CPU, 4 GB DDRII800 RAM (3 GB effective), X-Fi Platinum sound, GeForce 7600 GT, 1920x1440 resolution, 250 GB HDD, Visual C++ 2008 Express
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04-07-2009, 02:27 PM	#5
quzah +++ OK NO CARRIER Join Date: Oct 2001 Posts: 10,262	If you're writing your own (not using a library) method of outputting BMP files, I'd suggest going with TGA instead. They're much simpler to figure out. If you're looking for more file types: Wotsit.org Quzah. __________________ Hundreds of thousands of dipshits can't be wrong. Are you up for the suck?
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04-07-2009, 02:38 PM	#6
Maz Registered User Join Date: Nov 2005 Posts: 146	And if you just want to visualize the data aquired by a C program, dump values in a file, and use gnuplot to do the plotting. You can even write a script file doing the plotting using C, and launch gnuplot with simple system("") call. (or fork and exec). re-inventing the wheel can be cool and teach you a lot, but if the point is to get results... __________________ C:stä suomeksi A programmer's diary - all for C, all against OOP hype. (Eg. not against OOP, but against the hype) CWF Freeware
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