Added Makefile to heat1d and symlinks to heat2d.

dirt/heat1d/README.md

+# How to run the examples
+
+## Using pipe to chain the program ad Gnuplot
+
+Compile the code `sinwave.1c`
+
+```{bash}
+    gcc -c sinwave.c
+    gcc -c plot2d.c
+    gcc -o sinwave sinwave.o plot2d.o -lm
+```
+
+To run program with command pipe
+
+```{bash}
+    sinwave | gnuplot --persist sinwave.plt
+```
+
+Note, this may sometimes file due to the race conditon of the availability of
+data file `sinwave.dat` and the launch of `gnuplot`. Note, the commands on
+each side the of pipe `|` are executed in parallel.
+
+## Using pipe via system call inside the program
+
+Compile the code `sinwave1.c`
+
+```{bash}
+    gcc -c sinwave1.c
+    gcc -c plot2d.c
+    gcc -o sinwave1 sinwave1.o plot2d.o -lm
+```
+
+In this approch, a pipe is created via the call to system function `popen()`
+
+```{C}
+    ofifo = popen("gnuplot --persist","w");
+```
+
+The `gnuplot` commands, along with the data to plot are sent to the stream
+with statements
+
+```{C}
+    // Set output
+    fprintf(ofifo, "set term X11\n");
+    fprintf(ofifo, "set xrange[-1:1]\n");
+    fprintf(ofifo, "set yrange[0:1]\n");
+    ... ...
+    // Plot generated data, with '-' for data to feed plot
+    fprintf(ofifo, "plot '-' using 1:2 with lines;\n");
+    for (int i=0; i<n; i++)
+        fprintf(ofifo, "%f %f\n", x[i], y[i]);
+    fprintf(ofifo,"e\n");
+    fflush(ofifo);
+```
+
+The outpu setup can also be loaded from a file, e.g. `conf.plt`, containing
+
+```{bash}
+    set term X11
+    set xrange [0:2*pi]
+```
+
+Then simply run the program with the binary name
+
+```{bash}
+    sinwave1
+```
+

dirt/heat1d/plot.conf

+set term X11
+set xrange [-1:1]
+set yrange [0:1]
+unset key

dirt/heat2d/plot.conf

+# Plot config file for Gnuplot
+set term X11 size 1300, 720
+
+unset parametric
+set style data lines
+set zrange[-1:1]
+set view 40,120,1,1
+
+unset key
+unset border
+
+unset xtics
+unset ytics
+unset ztics
+unset colorbox
+set pm3d interpolate 0,0

dirt/heat2d/plot2d.c

+../common/plot2d.c
\ No newline at end of file

dirt/heat2d/plot2d.h

+../common/plot2d.h
\ No newline at end of file