查看“直方图”的源代码

IDL自带的HISTOGRAM可以运算直方图，然后用plot命令画出来
::* PSYM=10可画成直方图形式，但是缺少直方图的边框

[[astro_lib]]中的plothist；[[Coyote库]]中的cgplothist；

sdssidl中的plothist由于和[[astro_lib]]中的plothist重名，被改为sdssidl_plothist

== HISTOGRAM ==
 Result = HISTOGRAM( Array [, BINSIZE=value] [, INPUT=variable] [, LOCATIONS=variable] [, MAX=value] [, MIN=value] [, /NAN] 
 [, NBINS=value] [, OMAX=variable] [, OMIN=variable] [, /L64 |  REVERSE_INDICES=variable] ) 
*关键词 locations是bin的位置 = MIN + v*BINSIZE, with v = 0,1,...,NBINS-1.
*BINSIZE = (MAX – MIN) / (NBINS – 1) 

== plothist ==
  plothist, arr, xhist, yhist, [, BIN=, /FILL, /NOPLOT, /OVERPLOT, PEAK=,
                                     /AUTOBIN,  ...plotting keywords]
*不能设置min，max等关键词

== cghistoplot ==
  cgHistoplot, Fix(RandomU(seed, 200)*20), POLYCOLOR=['charcoal', 'steel blue'], /FILLPOLYGON

*可以用mininput，maxinput设置MIN，MAX; 
*locations,histdata关键词可给出Xbin和Yhist的数值
*颜色的处理很强大
*似乎没有直接画面积归一化的直方图功能

== sdssidl_plothist ==
 plothist, array, weights=,  peak=, norm=, aspect=, /error, nboot=, 
       /noplot, /overplot, /fill, fcolor=, /fline, forientation=, fpattern=, fspacing=
       xhist=, yhist=, reverse_indices=  ...plotting keywords...histogram keywords]

*直接支持plotting,histogram keywords的关键词，很强大，比如overplot功能
*norm，peak，weights的功能很贴心