;
pro log10f, x,spval
;
n = n_elements(x)
;print,'enter log10f: n=',n,' spval=',spval
nbad = 0
for i=0,n-1 do begin
  if x[i] ne spval then begin
    if (x[i] le 1.e-20) then begin
      nbad = nbad+1
      x[i] = spval 
    endif else x[i] = alog10(x[i])
  endif
endfor
;print,'log10f: n=',n,': found ',nbad,' data < 1.e-20'
end