# Function:s2surp

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## s2surp

Draw a colour surface representation of the 2-dimensional array, data, containing nx * ny values.

## Prototype

```void s2surp(float **data, int nx, int ny, int i1, int i2, int j1, int j2, float datamin, float datamax, float *tr); ```

## Description

Draw a colour surface representation of the 2-dimensional array, data, containing nx * ny values. A sub-section only of the array is drawn, viz. data[i1:i2][j1:j2]. Data values <= datamin are mapped to the first colour in the colour map (see s2scir), while values >= datamax are mapped to the last entry in the colour map. The mapping is linear at this stage. The final argument, tr, defines the transformation of the data cell locations to world coordinates in the X-Y space, and the transformation of data values to the Z ordinate, as follows:

• x = tr[0] + tr[1] * i + tr[2] * j
• y = tr[3] + tr[4] * i + tr[5] * j
• z = tr[6] + tr[7] * dataval

 s2scir Set the range of colour indices used for shading. s2surpa Draw a colour surface representation of the 2-dimensional array, data, containing nx * ny values.

## Code Example

```#include <stdio.h> #include <stdlib.h> #include <math.h> #include "s2plot.h" #define XLIMIT 10.0 #define YLIMIT 10.0 #define ZLIMIT 10.0 #define TWOPI 6.2831853 #define NX 64 #define NY 64 int main(int argc, char *argv[]) { float x1 = -XLIMIT, x2 = XLIMIT; /* x world coord range */ float y1 = -YLIMIT, y2 = YLIMIT; /* y world coord range */ float z1 = -ZLIMIT, z2 = ZLIMIT; /* z world coord range */ int i, j; /* Loop variables */ float **image; /* 2D array for image */ float minz = 9e30; /* Minimum value */ float maxz = -9e30; /* Maximum value */ float x, y, dx, dy; /* Temporary variables */ float tr[8]; /* Transformation matrix */ float tr2[12]; /* Transformation matrix */ s2opend("/?",argc,argv); /* Open the display */ s2swin(x1,x2,y1,y2,z1,z2); /* Set the window coordinates */ s2box("BCDET",0,0,"BCDET",0,0,"BCDET",0,0); /* Draw coordinate box */ dx = (x2-x1)/(float)(NX-1); /* Spacing in X */ dy = (y2-y1)/(float)(NY-1); /* Spacing in Y */ image = (float **)calloc(NX, sizeof(float *)); /* Allocate memory */ for (i=0;i<NX;i++) { image[i] = (float *)calloc(NY, sizeof(float)); /* Allocate memory */ x = i*dx + x1; for (j=0;j<NY;j++) { y = j*dy + y1; image[i][j] = sqrt(x*x + y*y); /* Data points */ minz = (image[i][j] < minz) ? image[i][j] : minz; maxz = (image[i][j] > maxz) ? image[i][j] : maxz; } } /* set up a unity transformation matrix */ tr[0] = x1; tr[1] = (x2-x1)/(float)(NX-1); tr[2] = 0.0; tr[3] = y1; tr[4] = 0.0; tr[5] = (y2-y1)/(float)(NY-1); tr[6] = z1; tr[7] = (z2-z1)/(maxz-minz); s2icm("rainbow", 1000, 1500); /* Install colour map */ s2scir(1000, 1500); /* Set colour range */ /* plot surface */ s2surp(image, NX, NY, 0, NX-1, 0, NY-1, minz, maxz, tr); /* plot the same data, but on the base-level z plane, using the * more general s2surpa function. */ tr2[0] = tr[0]; tr2[1] = tr[1]; tr2[2] = tr[2]; tr2[3] = 0.0; tr2[4] = tr[3]; tr2[5] = tr[4]; tr2[6] = tr[5]; tr2[7] = 0.0; tr2[8] = z1; tr2[9] = 0.0; tr2[10] = 0.0; tr2[11] = 0.0; /* new colormap and plot */ s2surpa(image, NX, NY, 0, NX-1, 0, NY-1, minz, maxz, tr2); s2show(1); /* Show the S2PLOT window */ return 1; } ```

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