diff --git a/swash/processing/post.py b/swash/processing/post.py
index 63c9935..2dbbf82 100644
--- a/swash/processing/post.py
+++ b/swash/processing/post.py
@@ -70,9 +70,9 @@ fig.tight_layout()
 
 fig_r, ax_r = plt.subplots()
 
-ax_r.plot(phi_eta[0], R)
+ax_r.plot(1/phi_eta[0], R)
 ax_r.autoscale(axis="x", tight=True)
-ax_r.set(ylim=(0, 1), xlabel="f (Hz)", ylabel="R")
+ax_r.set(ylim=(0, 1), xlabel="t (s)", ylabel="R")
 ax_r.grid()
 
 fig_x, ax_x = plt.subplots()