# Example 7 - a two-dimensional example using list output (Fortran)

```      PROGRAM CSEX07
C
C  Do a 2D approximation using a list of output coordinates.
C
C
C  The dimensionality of the problem.
C
PARAMETER (NDIM=2)
C
C  The number of input data points.
C
PARAMETER (NDATA=500)
C
C  The number of output data points in the X coordinate direction.
C
PARAMETER (NX=29)
C
C  The number of output data points in the Y coordinate direction.
C
PARAMETER (NY=25)
C
C  The number of output data points.
C
PARAMETER (NO=NX*NY)
C
C  The number of knots in the X direction.
C
PARAMETER (N1=10)
C
C  The number of knots in the Y direction.
C
PARAMETER (N2=10)
C
C  The size of the workspace.
C
PARAMETER (NCF=N1*N2, NWRK=NCF*(NCF+3))
C
C  Define error file, Fortran unit number, workstation type,
C  and workstation ID.
C
PARAMETER (IERRF=6, LUNIT=2, IWTYPE=1, IWKID=1)
C
C  Dimension the arrays.
C
DIMENSION XDATA(NDIM,NDATA),YDATA(NDATA),NODES(NDIM),WORK(NWRK)
DATA XMIN,YMIN,XMAX,YMAX / -1.4, -1.2, 1.4, 1.2/
REAL XO(NO),  YO(NO), OUTPUT(NO)
REAL XP(NX),  YP(NY), OPLOT(NX,NY)
C
C  Create the data array for the surface.
C
DO 10 I=1,NDATA
XDATA(1,I) = XMIN+(XMAX-XMIN)*DSRND1()
XDATA(2,I) = YMIN+(YMAX-YMIN)*DSRND1()
YDATA(I)   = XDATA(1,I) + XDATA(2,I)
T1 = 1.0/((ABS(XDATA(1,I)-0.1))**2.75 +
+                     ABS(XDATA(2,I))**2.75+0.09)
T2 = 1.0/((ABS(XDATA(1,I)+0.1))**2.75 +
+                     ABS(XDATA(2,I))**2.75+0.09)
YDATA(I) = 0.3*(YDATA(I)+T1-T2)
10 CONTINUE
C
C  Create the output arrays.
C
INDX = 0
DO 103 J=1,NY
DO 104 I=1,NX
INDX = INDX+1
XO(INDX) = XMIN+(REAL(I-1)/REAL(NX-1))*(XMAX-XMIN)
YO(INDX) = YMIN+(REAL(J-1)/REAL(NY-1))*(YMAX-YMIN)
104   CONTINUE
103 CONTINUE
C
C  Specify the numbers of nodes in each coordinate.
C
NODES(1) = N1
NODES(2) = N2
C
CALL CSA2LS (NDATA,XDATA,YDATA,NODES,NO,XO,YO,
+             OUTPUT,NWRK,WORK,IER)
C
C  Plot the 2D surface approximation.
C
C Open GKS and define the foreground and background color.
C
CALL GOPKS (IERRF, ISZDM)
CALL GOPWK (IWKID, LUNIT, IWTYPE)
CALL GACWK (IWKID)
C
C  Convert the linear output array to a 2D array.
C
DO 21 I=1,NX
DO 22 J=1,NY
OPLOT(I,J) = OUTPUT((J-1)*NX + I)
22   CONTINUE
21 CONTINUE
C
C  Create the output grid for plotting.
C
DO 105 I=1,NX
XP(I) = XMIN+(REAL(I-1)/REAL(NX-1))*(XMAX-XMIN)
105 CONTINUE
DO 106 J=1,NY
YP(J) = YMIN+(REAL(J-1)/REAL(NY-1))*(YMAX-YMIN)
106 CONTINUE
C
C  Plot the surface.
C
CALL TDEZ2D(NX, NY, XP, YP, OPLOT, 2.5, -154., 80., 6)
CALL FRAME()
C
C Close GKS.
C
CALL GDAWK (IWKID)
CALL GCLWK (IWKID)
CALL GCLKS
C
STOP
END
REAL FUNCTION DSRND1()
C
C  Random number generator.
C
DATA ISEED/1/
SAVE ISEED
C
ISEED = ISEED*1103515245 + 12345
IT = IAND(ISHIFT(ISEED,-16),32767)
C
DSRND1 = REAL(IT)/32767.
C
RETURN
END
```

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