;
;------------------------------------------------------------------
;
function ixfind, z,nz,val,del
;
; Find nearest index to val in z(nz), with increment del
; If not found, return -1
;
for i=0,nz-1 do begin
  if (val ge z(i)-0.5*del and val le z(i)+0.5*del) then return,i
endfor
return,-1
end