Creating Graphs in C++: A Beginner's Guide

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Discussion Overview

The discussion revolves around how to create graphs in C++ for a beginner who is transitioning from IDL. Participants explore various methods for plotting data, including using external libraries and tools, as well as the limitations of C++ in this context.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the syntax for plotting a simple x-y graph in C++, expressing uncertainty about whether C++ can create graphs like IDL.
  • Another participant notes that C++ does not have a built-in GUI library and suggests several options, including writing data files for external plotting tools like Excel or Gnuplot, or using GUI toolkits such as Qt or wxWidgets.
  • A participant acknowledges the difficulty of writing data out as an image file and discusses the possibility of using a plotting library or doing it manually, emphasizing that this approach may be suitable for heavy number crunching tasks.
  • There is a suggestion that using Gnuplot could be the easiest way to produce publication-quality figures, mentioning its C++ interface and the option to call it directly from a program.
  • Another participant proposes that C++ implementations likely have graphics libraries and describes a low-level approach to graphics programming, including enabling graphics mode and defining a coordinate system.

Areas of Agreement / Disagreement

Participants generally agree that C++ lacks built-in graphing capabilities and that external libraries or tools are necessary for plotting. However, there are differing opinions on the best approach to take, with some favoring high-level libraries and others suggesting low-level programming techniques.

Contextual Notes

Participants mention various external tools and libraries without reaching a consensus on which is the most effective or user-friendly for beginners. There is also a lack of clarity on the specific capabilities of different C++ implementations regarding graphics.

taylrl3
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Hi,

I have just started to learn C++ after a year programming with IDL. I realize this is probably a really stupid thing to be asking but what syntax should I use to display my data. To start off with I just want to plot a simple x-y graph. I have my arrays all ready, what do I type? Can C++ even create graphs like IDL can? I'm sure it must.

Cheers
 
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C++ doesn't have a built in gui library.

You have a few options.
Write a data file and plot it with Excel/Gnuplot/etc
Write the data into an image file and display that
Learn Qt,wxWidgets or some other gui toolkit.
 
Thanks! I had the feeling it couldn't produce graphs directly.
How would I go writing the data out as an image file? Can I include axis etc like this?
 
taylrl3 said:
How would I go writing the data out as an image file? Can I include axis etc like this?
That's possibly the hardest option, you would either do it all yourself (the image is ulimtately just an array of values) or use some plotting library that could also plot to an image.
But it's a good option if you are doing some heavy number crunching type work and just need to output a map of some values.

Easiest is probably gnuplot if you need to produce publication type figures, it has a C++ interface (gunplot++) but haven't used it. You can also call it directly from your program using popen() to run the gnuplot command.

See also http://stackoverflow.com/questions/492893/graph-drawing-c-library
ps. If you are searching it's better to look for 'plot' than 'graph', in CS a graph is generally used in the maths sense, eg a heirachy of data
 
Last edited by a moderator:
taylrl3 said:
Hi,

I have just started to learn C++ after a year programming with IDL. I realize this is probably a really stupid thing to be asking but what syntax should I use to display my data. To start off with I just want to plot a simple x-y graph. I have my arrays all ready, what do I type? Can C++ even create graphs like IDL can? I'm sure it must.

Cheers

Surely your C++ implementation has a graphics library. I say that because I've done a lot of C++ graphics programming. And you can always create your own library with low-level (assembly) constructs by writing directly to the video memory of the output device. It's a large array. Put the right number in the right location of the array, and a pixel corresponding to that location lights up on the screen. Then take it from there although that's quite involved. Usually, though just find the high-level routines. In general it goes something like this:

enable graphics mode

define coordinate system

draw axes and labels

use SetPoint or Line command to draw curves in established coordinate system
 
Last edited:

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