This compiles and might be better:
// 2d interpolation
void setup() {
Serial.begin(9600);
}
void loop() {
int tpsaxis[] = { 0, 5, 10, 50, 60, 80, 90, 95, 97, 100,}; // 10
int rpmaxis[] = {1000,2000,3000,4000,5000,7000,8000,10000,12000,13500}; // 10
int tpso[10][10] = {
100, 100, 100, 100, 100, 100, 100, 100, 100, 100,
97, 97, 97, 97, 97, 97, 97, 97, 97, 97,
97, 97, 97, 97, 97, 97, 97, 97, 97, 97,
97, 97, 97, 97, 97, 97, 97, 97, 97, 97,
40, 40, 40, 40, 40, 40, 40, 40, 40, 40,
30, 30, 30, 30, 30, 30, 30, 30, 30, 30,
30, 30, 30, 30, 30, 30, 30, 30, 30, 30,
30, 30, 30, 30, 30, 30, 30, 30, 30, 30,
30, 30, 30, 30, 30, 30, 30, 30, 30, 30,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0}; // [ 9 x 9 ] matrix
int tpsout;
tpsout = multimap2d(4000, 50, rpmaxis, tpsaxis, tpso);
Serial.println(tpsout);
}
int multimap2d(int xval, int yval, int* xaxis, int* yaxis, int zvalues [10] [10] )
{
byte xpos = 1;
byte xi = 0;
byte ypos = 1;
byte yi = 0;
// deal with special cases first
if (xval <= xaxis[0])
{
xpos = 0 ;
xi=0 ; // then no interpolation is required.
}
else if (xval >= xaxis[9])
{
xpos = 9;
xi=0; // then no interpolation is required.
}
else
{
//search right interval
// uint8_t pos = 1; // have already established that we're not at xaxis[0] use xpos=1
while(xval > xaxis[xpos]) xpos++; // search until xpos found
// this will handle all exact "points" in the xaxis array
if (xval == xaxis[xpos])
{
xi=0; // no interpolation is required in x.
}
else
{
xi=1; // If above doesn't solve then interpolation is required using xpos and xpos-1
}
}
// do the same for yaxis
// deal with special cases first
if (yval <= yaxis[0])
{
ypos = 0;
yi=0; // then no interpolation is required.
}
else if (yval >= yaxis[9])
{
ypos = 9;
yi=0 ;// then no interpolation is required.
}
else
{
//search right interval
// have already established that we're not at yaxis[0] use ypos = 1
while(yval > yaxis[ypos]) ypos++; // search until ypos found
// this will handle all exact "points" in the _in array
if (yval == yaxis[ypos])
{
yi=0; // no interpolation is required in y.
}
else
{
yi=1; // If above doesn't solve then interpolation is required using ypos and ypos-1
}
}
// case 1. There is an exact point in the table
if(xi==0 && yi==0) return zvalues[xpos] [ypos];
// case 2. Interpolate in x only. i.e. yval corresponds to bounds or a breakpoint
if(xi==1 && yi==0)
{
return map(xval, xaxis[xpos-1], xaxis[xpos], zvalues[xpos-1] [ypos], zvalues[xpos] [ypos]);
}
// case 3.
if(xi==0 && yi==1)
{
return map(yval, yaxis[ypos-1],yaxis[ypos], zvalues[xpos] [ypos-1], zvalues[xpos] [ypos]);
}
//case 4. Interpolate both. x first
// if(xi==1 & yi==1)
else
{
int _high = map(xval, xaxis[xpos-1],xaxis[xpos], zvalues[xpos-1] [ypos], zvalues[xpos] [ypos]);
int _low = map(xval, xaxis[xpos-1],xaxis[xpos], zvalues[xpos-1] [ypos-1], zvalues[xpos] [ypos-1]);
return map(yval, yaxis[ypos-1],yaxis[ypos],_low,_high);
}
}