--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/+time/+rk/get_rk4_time_step.m	Thu Nov 15 16:42:58 2018 -0800
@@ -0,0 +1,21 @@
+% Calculate the size of the largest time step given the largest evalue for a operator with pure imaginary e.values.
+function k = get_rk4_time_step(lambda,l_type)
+    default_arg('l_type','complex')
+
+    rad = abs(lambda);
+    if strcmp(l_type,'real')
+        % Real eigenvalue
+        % kl > -2.7852
+        k = 2.7852/rad;
+
+    elseif strcmp(l_type,'imag')
+        % Imaginary eigenvalue
+        % |kl| < 2.8284
+        k = 2.8284/rad;
+    elseif strcmp(l_type,'complex')
+        % |kl| < 2.5
+        k = 2.5/rad;
+    else
+        error('l_type must be one of ''real'',''imag'' or ''complex''.')
+    end
+end
\ No newline at end of file