图自动这使得C code地块 [英] Making C code plot a graph automatically

问题描述

我已经写了一个程序，它用的，然后使用gnuplot的单独绘制它打算写入数据的列表为'.DAT'文件。有没有让我的code自动绘制它的一种方式？我的输出形式为：

I have written a program which writes a list of data to a '.dat' file with the intention of then plotting it separately using gnuplot. Is there a way of making my code plot it automatically? My output is of the form:

x-coord    analytic    approximation
x-coord    analytic    approximation
x-coord    analytic    approximation
x-coord    analytic    approximation
x-coord    analytic    approximation
 ....

在理想情况下，当我运行code曲线也将印有X标记，Y标签和标题（可从我的C code更改）。非常感谢。

Ideally, when I run the code the graph would also be printed with an x-label, y-label and title (which could be changed from my C code). Many thanks.

推荐答案

我碰到这个而前来寻找关于gnuplot的东西。尽管这是一个老问题，我想我会贡献一些示例code。我用这个我的一个程序，我想它做了pretty整洁的工作。据我所知，这PIPEing仅适用于Unix系统（参见下面的Windows用户编辑）。我gnuplot的安装是默认从Ubuntu库安装。

I came across this while searching for something else regarding gnuplot. Even though it's an old question, I thought I'd contribute some sample code. I use this for a program of mine, and I think it does a pretty tidy job. AFAIK, this PIPEing only works on Unix systems (see the edit below for Windows users). My gnuplot installation is the default install from the Ubuntu repository.

#include <stdlib.h>
#include <stdio.h>
#define NUM_POINTS 5
#define NUM_COMMANDS 2

int main()
{
    char * commandsForGnuplot[] = {"set title \"TITLEEEEE\"", "plot 'data.temp'"};
    double xvals[NUM_POINTS] = {1.0, 2.0, 3.0, 4.0, 5.0};
    double yvals[NUM_POINTS] = {5.0 ,3.0, 1.0, 3.0, 5.0};
    FILE * temp = fopen("data.temp", "w");
    /*Opens an interface that one can use to send commands as if they were typing into the
     *     gnuplot command line.  "The -persistent" keeps the plot open even after your
     *     C program terminates.
     */
    FILE * gnuplotPipe = popen ("gnuplot -persistent", "w");
    int i;
    for (i=0; i < NUM_POINTS; i++)
    {
    fprintf(temp, "%lf %lf \n", xvals[i], yvals[i]); //Write the data to a temporary file
    }

    for (i=0; i < NUM_COMMANDS; i++)
    {
    fprintf(gnuplotPipe, "%s \n", commandsForGnuplot[i]); //Send commands to gnuplot one by one.
    }
    return 0;
}

修改

在我的申请，我也碰到了，该地块没有出现，直到调用程序被关闭的问题。为了解决这个问题，添加 fflush（gnuplotPipe）你用过之后 fprintf中来发送你的最后一个命令。

In my application, I also ran into the problem that the plot doesn't appear until the calling program is closed. To get around this, add a fflush(gnuplotPipe) after you've used fprintf to send it your final command.

我也看到，Windows用户可以使用 _popen 在的popen 的 - 不过，我可以' t请确认这个，因为我不已经安装了Windows。

I've also seen that Windows users may use _popen in place of popen -- however I can't confirm this as I don't have Windows installed.

编辑2

一个可以避免通过发送gnuplot的在情节写入文件 ​​- 命令后面的数据点后面的字母E。

One can avoid having to write to a file by sending gnuplot the plot '-' command followed by data points followed by the letter "e".

例如

fprintf(gnuplotPipe, "plot '-' \n");
int i;

for (int i = 0; i < NUM_POINTS; i++)
{
  fprintf(gnuplotPipe, "%lf %lf\n", xvals[i], yvals[i]);
}

fprintf(gnuplotPipe, "e");

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