program define lott
    version 4.0

    preserve 
    clear

    gph open
    gph pen 1

    quietly{
        global ndraws=0
        global npairs=0
        global fract=0
        set obs 50
        gen x=(mod(_n-1,10)+1)/10
        gen y=1-int((_n-1)/10)/5
        gen str2 z=string(_n)
        gen xx=.
        gen yy=.
        gen x1=.
        gen y1=.
        gen str2 z1= string(_n) in 1/6}

    set graphics off
    graph y x, s(i) xlab(0,1) ylab(0,1) bbox(3000,0,23000,24000,850,400,0)
    set graphics on
    gphconv

    gph close
    gph open
    gph pen 1

    global D_sm1 "# draws"
    global D_sm2 "# with pairs"
    global D_sm3 "Rel freq"

    wdctl static D_sm1           5  80 40 10
    wdctl static ndraws         47  80 20 10
    wdctl static D_sm2           5  95 40 10 
    wdctl static npairs         47  95 20 10
    wdctl static D_sm3           5 110 40 10
    wdctl static fract          47 110 20 10

    wdctl button "Draw"           5  5 60 12 HJN_B1
    wdctl button "Draw n Times"   5 20 60 12 HJN_B3
    wdctl button "Help"           5 35 60 12 HJN_B5
    wdctl button "Close"          5 50 60 12 HJN_B6
        
    global D_sm4 "n"
    global HJN_V1=10
    wdctl static D_sm4   5 65 20 12 
    wdctl edit   HJN_V1 30 65 20 12

    global HJN_B1 "lottdr 0"
    global HJN_B3 "lott10"
    global HJN_B5 "whelp lott"
    global HJN_B6 "lottdr 1"

    lottdr 0

    noi wdlg "Lottery"  5 5 70 140

    gph close

    restore

end

program define lott10
    version 4.0

    if $HJN_V1 < 1 | $HJN_V1 > 200  {
        sstopbox stop "Number of draws must be between 1 and 200"
        exit}

    local i=1
    while `i'<=$HJN_V1 {
        lottdr 0
        wdupdate
        local i=`i'+1}

end

program define lottdr
    version 4.0

    local arg=`1'

    if `arg'==1 {
        replace x1=.
        replace x1=real(z1)
        sort x1
        local i=1
        while `i'<= 6 {
            local xval=(`i')/6.
            local zval=x1[`i']
            drtext `xval' 0 0 `zval'
            local i=`i'+1}
        gph text 1000 16000 0 0 # of draws=$ndraws, # with pairs=$npairs, relative frequency=$fract
        exit 1234}

    gph close
    gph open
    gph pen 1

    global ndraws=$ndraws+1

    points2 x y 1000 1
    texts x y z

    replace xx=uniform()
    replace yy=_n
    replace x1=.
    replace y1=.

    local i=1
    while `i' <= 6 {

*   Get random integer, i1, in (1,50-i+1):

        local i5=50-`i'+1
        local i1=int(`i5' * xx[`i'])+1
        
*   Now trade yy[i1] with yy[i5]:

        local i3=yy[`i1']
        replace yy=yy[`i5'] in `i1'
        replace yy=`i3' in `i5'

        replace x1=x[`i3'] in `i'
        replace y1=y[`i3'] in `i'
        replace z1=z[`i3'] in `i'
    
        local i=`i'+1}     

    gph pen 3
    points2 x1 y1 1000 1
    texts x1 y1 z1

    replace x1=.
    replace x1=real(z1)
    sort x1
    local pairs=0
    local i=1
    while `i'<= 5 {
        local i1=`i'+1
        if abs(x1[`i']-x1[`i1']) < 1.5 {local pairs=1}
        local i=`i'+1}
    if `pairs'==1 {global npairs=$npairs+1}
    global fract: display %5.3f $npairs/$ndraws
    gph text 2000 16000 0 0 Draw # $ndraws

end
exit