Problem with Matlab's subplot

When I plot an oscillatory function in Matlab using subplot, it is much less accurate than when i use the plot function. That is, when I use plot there are maybe 15 condensed oscillations, but in subplot there are only 5, spread out. I believe the error is caused because the number of points used to approximate the values of the function is less for subplot than plot. Note that I am doing the plotting with the ezplot function, because the function is symbolic. Any idea how to change the number of points used? Or if it is a different problem entirely?