我已经制作了一些数据，我的目的是绘制它。为方便起见，我已经定义了一个管道，并通过这个管道将plot命令传递给GNUplot，命令为：
load "file.gnu"
但是我注意到图中缺少数据文件中的一些数据点。当我通过终端启动GNUplot并使用相同的命令绘制时，没有丢失点这样的问题。管道内存有限吗？我对这种情况感到困惑，并希望收到你对此事的看法。
编辑：源文件如下（取消注释管道部分）：
//Compilation: gcc Q5.c -lm -o Q5
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#define lowbnd 2.5
#define upbnd 10.0
#define precision 100.0
// Gamma function is defined in the GNU C library so we use it
double approx1(double x)
{
return sqrt(2 * M_PI / x) * pow(x, x) * exp(-(x - 1 / (12.0 * x) + 1 / (pow(x, 3) * 360.0)));
}
double approx2(double x)
{
return tgamma(x + 5) / ( (x + 4) * (x + 3) * (x + 2) * (x + 1) * x );
}
int main(void)
{
FILE *fp = fopen("Q5data.dat", "w+");
int i;
double x, y1, y2, yexact, diff1, diff2;
for(i = 0; x < upbnd; i++)
{
x = lowbnd + i / precision;
y1 = approx1(x);
y2 = approx2(x);
yexact = tgamma(x);
diff1 = fabs(y1 - yexact);
diff2 = fabs(y2 - yexact);
fprintf(fp, "%f \t %f \t %f \t %f \t %e \t %e \n", x, y1, y2, yexact, diff1, diff2);
}
// The below line works well but through piping some data points were lost so I commented this section out. You may try
// it yourself and see.
FILE *gp = popen("gnuplot -persist","w");
if (gp==NULL)
{
printf("Error opening pipe to GNUplot. Check if you have it! \n");
exit(0);
}
fprintf(gp, "load 'Q5.gnu' \n");
puts("Please check the generated plot files named Q5.ps and Q5diff.ps");
// Just to try how well these represent the gamma function
//x = 35;
//printf("%f \n %f \n %f \n", tgamma(x), approx1(x), approx2(x));
pclose(gp);
fclose(fp);
return 0;
}
PLOT脚本：
set key below Left title 'Legend' box 3
set logscale
set terminal postscript enhanced color font 'Euclid, 15'
set border linewidth 1.5
set title "Gamma fnc. and Approximations" tc rgb"red"
set pointsize 1.0
set xrange [2.5:10.0]
set autoscale y
set xtics autofreq
set xlabel "x" tc rgb"green"
set ylabel "" tc rgb"green"
set grid xtics ytics mxtics nomytics
set output "Q5log.ps"
plot "Q5data.dat" u 1:2 t 'Approximation 1' lc rgb"blue" with lines, \
"Q5data.dat" u 1:3 t 'Approximation 2' lc rgb"red" with lines, \
"Q5data.dat" u 1:4 t 'Exact' lc rgb"cyan" with lines
set output "Q5difference.ps"
set title "Difference btw. Approximations and Exact Representation"
plot "Q5data.dat" u 1:5 t 'Difference 1' lc rgb"blue" with lines, \
"Q5data.dat" u 1:6 t 'Difference 2' lc rgb"red" with lines
set output "Q5nonlog.ps"
unset logscale
plot "Q5data.dat" u 1:2 t 'Approximation 1' lc rgb"blue" with lines, \
"Q5data.dat" u 1:3 t 'Approximation 2' lc rgb"red" with lines, \
"Q5data.dat" u 1:4 t 'Exact' lc rgb"cyan" with lines
由于