/* element of projection --> multplication of (redshifted by cr_z) spectrum
* and the filter */
float rb_pixel(float lambda)
{
float sl,spectrum;
unsigned long i,ip1;
k_locate(rb_lambda, rb_nl, lambda, &i);
if(i>=rb_nl-1 || i<0) return(0.);
ip1=i+1;
sl=(lambda-rb_lambda[i])/(rb_lambda[ip1]-rb_lambda[i]);
spectrum=rb_spectrum[i]+sl*(rb_spectrum[ip1]-rb_spectrum[i]);
return(spectrum);
} /* end filter */
/* linear interpolate in a given vector; out of bounds --> 0 */
float k_interpolate(float currpos,
float vals[],
float pos[],
IDL_LONG n)
{
unsigned long i,ip1;
float sp,currval;
k_locate(pos, (unsigned long) n, currpos, &i);
if(i>=n-1) return(vals[n-1]);
if(i<0) return(vals[0]);
ip1=i+1;
sp=currpos-pos[i];
currval=vals[i]+sp*(vals[ip1]-vals[i])/(pos[ip1]-pos[i]);
return(currval);
} /* end interpolate templates */