diff -up plplot-5.9.9/examples/lua/x04.lua.lua52 plplot-5.9.9/examples/lua/x04.lua
--- plplot-5.9.9/examples/lua/x04.lua.lua52	2013-08-07 16:17:30.347353816 -0600
+++ plplot-5.9.9/examples/lua/x04.lua	2013-08-07 17:00:45.658739651 -0600
@@ -56,7 +56,7 @@ function plot1(type)
   for i=1, 101 do
     freql[i] = -2 + (i-1) / 20
     freq = 10^freql[i]
-    ampl[i] = 20 * math.log10(1 / math.sqrt(1 + (freq / f0)^2))
+    ampl[i] = 20 * math.log(1 / math.sqrt(1 + (freq / f0)^2),10)
     phase[i] = -(180 / math.pi) * math.atan(freq / f0)
   end
 
diff -up plplot-5.9.9/examples/lua/x26.lua.lua52 plplot-5.9.9/examples/lua/x26.lua
--- plplot-5.9.9/examples/lua/x26.lua.lua52	2013-08-07 16:17:30.349353808 -0600
+++ plplot-5.9.9/examples/lua/x26.lua	2013-08-07 17:01:06.456662737 -0600
@@ -106,7 +106,7 @@ function plot1(type, x_label, y_label, a
   for i = 1, 101 do
     freql[i] = -2 + (i-1)/20
     freq = 10^freql[i]
-    ampl[i] = 20 * math.log10(1/math.sqrt(1+(freq/f0)^2))
+    ampl[i] = 20 * math.log(1/math.sqrt(1+(freq/f0)^2),10)
     phase[i] = -180/math.pi*math.atan(freq/f0)
   end