#!/usr/bin/env bash
set -euo pipefail
export GMT_SESSION_NAME=$$
mkdir -p figures
gmt begin figures/GMT-17-004 png,pdf E200,H2,Qg4,Qt4 -C
gmt set GMT_AUTO_DOWNLOAD off MAP_FRAME_TYPE plain PROJ_LENGTH_UNIT cm FONT_ANNOT_PRIMARY 9p FONT_LABEL 10p FONT_TITLE 11p PS_LINE_CAP round PS_LINE_JOIN round COLOR_NAN gray85
gmt grdmath -R-4/4/-4/4 -I0.1 X 1 SUB SQR Y 0.5 SUB SQR ADD NEG EXP 2 MUL X 1.4 ADD SQR Y 0.8 ADD SQR ADD -0.7 MUL EXP 1.5 MUL SUB = field.nc
gmt grdmath field.nc DDX = slope.nc
gmt makecpt '-C#00549f,white,#f6a800' -T-2/2/0.1 -Z -H > field.cpt
gmt grdimage slope.nc -R-4/4/-4/4 -JX11c -Cfield.cpt -E200 -nc -Bxa2+lx -Bya2+ly -BWSne
gmt colorbar -Cfield.cpt -DJBC+w8c/0.3c+h+o0/0.9c -Bxa1+lDerivative
gmt basemap -B+t"GMT-17-004"
gmt end