function histograma,y,nbins=nbins,binsize=binsize,x=x,cum=cum,ind=ind,forcex=forcex ;+ ; ; Calculates an histogram of the vector y. ; ; IN: y - fltarr vector ; ; KEYWORDS: nbins - number of bins to be used (default is 10) ; This value is ignored if binsize is provided. ; ; binsize - size of the bin to use (otherwise chosen to span the ; range of y with 10 elements) ; x - vector with the centers of the intervals ; used to calculate the histogram. An element of ; y is included in bin i when ; ; x(i)-binsize/2. <= y(i) < x(i)+binsize/2. ; ; This array is internally created, unless forcex is set, ; in which case the input array is adopted. ; ; cum - when switched on, a cumulative distrib. is returned ; ; ind - an optional array with the indices of the elements ; in the input array in each bin (padded with -1s). ; ; forcex -- set this keyword to impose an input x array, ; otherwise x is internally created and replaces the input one. ; ; Carlos Allende Prieto, UT, Sep 1999 ; , UT, April 2005, changed to use long integers ; , A&M, October 2010, added cum keyword ; , Radazul, June 2011, added nbins and ind keywords, ; changed nbins default and allowed x to be an input ; even if it doesn't contain all elements of y, ; as long as x is equidistant, when setting xforce. ;- ; if keyword_set(forcex) then begin nbins=n_elements(x) if nbins lt 2 then begin print,'% HISTOGRAMA: The intput x array must have at least 2 elements. I quit!' return,-1 endif binsize=x[1]-x[0] delta=x-shift(x,1) delta=delta[1:n_elements(delta)-1] if max(delta)-min(delta) gt 1d-3*mean(delta) then begin print,'% HISTOGRAMA: The intput x array is not equidistantly spaced. I quit!' stop return,-1 endif endif else begin if not keyword_set(nbins) then nbins=10 if not keyword_set(binsize) then binsize=(max(y)-min(y))/float(nbins) else \$ nbins=ceil((max(y)-min(y))/binsize) left=nbins*binsize-(max(y)-min(y)) if (nbins eq 0) then nbins=1 x=findgen(nbins)*binsize+min(y)-left/2.+binsize/2. endelse hist=lonarr(nbins) if arg_present(ind) then begin ind=lonarr(nbins,n_elements(y),/nozero) ind[*]=-1 endif for i=0l,nbins-1 do begin pos=where(y ge x(i)-binsize/2. and y lt x(i)+binsize/2.) if (i eq nbins-1) then \$ pos=where(y ge x(i)-binsize/2. and y le x(i)+binsize/2.) if (max(pos) ne -1) then hist(i)=n_elements(pos) if keyword_set(cum) and i gt 0 then hist(i)=hist(i-1)+hist(i) if n_elements(ind) gt 0 then ind[i,0:n_elements(pos)-1]=pos endfor return,hist end