program define histgm
    version 4.0

    local y     = "`1'"
    local xmin  = `2'
    local xmax  = `3'
    local nbins = `4'

    local del = (`xmax'-`xmin')/`nbins'

    tempvar x1 x2 y1 y2

    gen `x1' = `xmin' + (_n)*`del' in 1/`nbins'
    gen `y1'=.
    gen `y2'=.
    gen `x2'=.

    replace `y1' = int(`nbins'* (`y'-`xmin')/(`xmax'-`xmin'))+1
    replace `y1'=min(`y1',`nbins')
    replace `y1'=max(`y1',1)

    local i = 1
    while `i' <= `nbins' {

        count if `y1'==`i'
        replace `y2' = _result(1) in `i'
        local i=`i'+1}

    replace `y2' = `y2'/((_N)*`del')
    replace `y1' = 0
    replace `x2' = `x1'-`del'

*    gph text 6000 16000 0 0 After replaces


    segments `x1' `y1' `x1' `y2'
    segments `x2' `y1' `x2' `y2'
    segments `x1' `y2' `x2' `y2'
    segments `x1' `y1' `x2' `y1'

end