FUNCTION Trig2D,n,m,XSIZE=xsize,YSIZE=ysize
;+
;z=Trig2D(n,m) returns a spatial cosine with n horizontal
;and m vertical cycles. The default size is 256x256.
;The size can be set to any integer value using
;keywords XSIZE and YSIZE.
;
;z=Trig2D(2,3,XSIZE=100,YSIZE=200) returns an array
;of size 100 columns and 200 rows with 2 horizontal and
;three vertical cycles.
;
;EXAMPLE
;The results could be computed and displayed with
;n=2 & m=3 & xsize=100 & ysize=200
;z=Trig2D(n,m,XSIZE=xsize,YSIZE=ysize)
;txt=STRING(FORMAT='("N=",I2," M=",I2)',n,m)
;WINDOW,/FREE,XSIZE=xsize,YSIZE=ysize,TITLE=txt
;TVSCL,z
;
;H. Rhody, July 2000
;-

IF N_PARAMS() LT 2 THEN $
	MESSAGE,'Two arguments required'
IF NOT KEYWORD_SET(xsize) THEN xsize=256
IF NOT KEYWORD_SET(ysize) THEN ysize=256
x=FINDGEN(xsize,1)#MAKE_ARRAY(1,ysize,VALUE=1)/(xsize-1)
y=((ysize-1)-MAKE_ARRAY(xsize,1,value=1)#FINDGEN(1,ysize))/(ysize-1)
RETURN,COS(2*!PI*(n*x+m*y))
END