Gnuplot 和 C - plot 不同的符号/颜色

Question

I would like to plot different points with different colors and symbols. Here is my Code in "C":

float x[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11};
float y[] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11};

FILE *gnuplot = popen("gnuplot", "w");

fprintf(gnuplot, "plot '-' pt 7 pointsize 2 lc \"blue\" notitle \n");

for (int i = 0; i < 6; ++i) {

    fprintf(gnuplot,"%f %f\n", x[i], y[i]);
}

fprintf(gnuplot, "plot '-' pt 5 pointsize 2 lc \"red\" notitle \n");

for (int i = 6; i < 12; ++i) {

    fprintf(gnuplot,"%f %f\n", x[i], y[i]);
}

fprintf(gnuplot, "e\n");
fflush(gnuplot);
getch();
fclose(gnuplot);

Unfortunately, all points have the same type and same color. What is my mistake? Thanks in advance!

Edit:

Result of the code

All points are blue and have the pointtype 7 and the pointsize 2. The second command line to change the style has no effect:

    fprintf(gnuplot, "plot '-' pt 5 pointsize 2 lc \"red\" notitle \n");

Answer 1

Your code is like the following:

plot '-' pt 7 ps 2 lc "blue" notitle
0    0
1    1
2    2
3    3
4    4
5    5
plot '-' pt 6 ps 2 lc "red" notitle
6    6
7    7
8    8
9    9
10   10
11   11
e

For inline data, ie special filename '-' the data is ended by a line e . Check help special-filenames .

So, your code will:

• plot x from 0 to 5 with blue filled circles
• the line plot '-' pt 6 ps 2 lc "red" notitle will be interpreted as data line because inline data has not yet been ended by a line e , hence, this line will be ignored because it does not contain numerical data
• plot x from 6 to 11 with blue filled circles

But it seems you want to have the following:

Code:

plot '-' pt 7 ps 2 lc "blue" notitle, \
     '-' pt 6 ps 2 lc "red"  notitle
0    0
1    1
2    2
3    3
4    4
5    5
e
6    6
7    7
8    8
9    9
10   10
11   11
e

Result:

Addition : (as mentioned in the comments)

Since gnuplot 5.0 you have datablocks which are including the data as well into the plotting code, check help inline . The advantage is that if you want to make plots of several columns you don't have to provide the data multiple times or split it into sequential 2 column data. The following examples will all result in the same plot:

Code:

$Data1 <<EOD
0    0
1    1
2    2
3    3
4    4
5    5
EOD

$Data1 <<EOD
6    6
7    7
8    8
9    9
10   10
11   11
EOD

plot $Data1 u 1:2 w p pt 7, \
     $Data2 u 1:2 w p pt 5

$Data <<EOD
0    0    6    6
1    1    7    7
2    2    8    8
3    3    9    9
4    4    10   10
5    5    11   11
EOD

plot $Data u 1:2 w p pt 7, \
        '' u 3:4 w p pt 5

plot '-' u 1:2 w p pt 7, \
     '-' u 1:2 w p pt 5,
0    0
1    1
2    2
3    3
4    4
5    5
e
6    6
7    7
8    8
9    9
10   10
11   11
e

plot '-' u 1:2 w p pt 7, \
     '-' u 3:4 w p pt 5,
0    0    6    6
1    1    7    7
2    2    8    8
3    3    9    9
4    4    10   10
5    5    11   11
e
0    0    6    6
1    1    7    7
2    2    8    8
3    3    9    9
4    4    10   10
5    5    11   11
e