Add splines figure and script

doc/rst/source/sample1d.rst

@@ -101,6 +101,14 @@ Optional Arguments
  You may optionally evaluate the first or second derivative of the spline
  by appending **+d1** or **+d2**, respectively.
 
+.. figure:: /_images/GMT_splines.*
+ :width: 500 px
+ :align: center
+
+ The |-F| option lets you choose among several interpolators, including
+ one that is approximate (the smoothing spline). You can also specify
+ that you actually need a derivative of the solution instead of the value.
+
 .. _-N:
 
 **-N**\ *col*

doc/scripts/GMT_splines.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+#
+# Show all splines and their derivatives for a basic data set
+cat << EOF > t.txt
+0 0
+1 1
+2 1.5
+3 1.25
+4 1.5
+4.5 3
+5 2
+6 2.5
+EOF
+# Splines
+gmt begin GMT_splines
+ gmt basemap -R-0.1/6.1/-0.1/3.1 -JX15c/6c -Baf+l"u" -By+l"u(x)" -BWSne
+ gmt sample1d t.txt -T0.01 -Fc | gmt plot -W1p -l"Cubic spline (-Fc)"
+ gmt sample1d t.txt -T0.01 -Fs1 | gmt plot -W1p,orange -l"Smooth cubic spline (-Fs1)"
+ gmt sample1d t.txt -T0.01 -Fl | gmt plot -W1p,blue -l"Linear spline (-Fl)"
+ gmt sample1d t.txt -T0.01 -Fa | gmt plot -W1p,red -l"Akima spline (-Fa)"
+ gmt sample1d t.txt -T0.01 -Fn | gmt plot -W1p,darkgreen -l"Nearest neighbor (-Fn)"
+ gmt plot t.txt -Sc0.25c -Gred -Wthin -l"Data"
+ gmt legend -DjTL+w4.9c+o0.2c -F+p1p+gwhite+s 
+gmt end show

doc/scripts/images.dvc

@@ -1,5 +1,5 @@
 outs:
-- md5: b6459673d7a8a0b6ba470a48598b5492.dir
- size: 32703171
- nfiles: 198
+- md5: 0f6e11c68f7bc763f96af35c134b3b93.dir
+ size: 32734813
+ nfiles: 199
  path: images