courseraのmachine learning講座をやりはじめたのですが、week2のプログラミング課題の任意課題（ex1_multi）を実行すると下記のようにwarningが発生してしまいます。
原因はなんでしょうか？宜しくお願いします。

Loading data ...
First 10 examples from the dataset:
 x = [2104 3], y = 399900
 x = [1600 3], y = 329900
 x = [2400 3], y = 369000
 x = [1416 2], y = 232000
 x = [3000 4], y = 539900
 x = [1985 4], y = 299900
 x = [1534 3], y = 314900
 x = [1427 3], y = 198999
 x = [1380 3], y = 212000
 x = [1494 3], y = 242500
Program paused. Press enter to continue.
Normalizing Features ...
Running gradient descent ...
Theta computed from gradient descent:
 NaN
 NaN
 NaN

Predicted price of a 1650 sq-ft, 3 br house (using gradient descent):
 $0.000000
Program paused. Press enter to continue.
warning: opengl_renderer: data values greater than float capacity.  (1) Scale da
ta, or (2) Use gnuplot
warning: called from
    ex1_multi at line 117 column 1
Solving with normal equations...
Theta computed from the normal equations:
 89597.909541
 139.210674
 -8738.019112

Predicted price of a 1650 sq-ft, 3 br house (using normal equations):
 $0.000000

warning: opengl_renderer: data values greater than float capacity. (1) Scale data, or (2) Use gnuplot