Doug

I am trying to reproduce the approach in the book Programming Collective
Intelligence,
for building up a dataset. The author uses nested hash tables.

The idea is to collect peoples responses, setting the nested table to the
reponse and its value 1.

The $allItems hashtable is all the respones collected.

Then iterate over the $hash inserting the 'missing' values.
That is adding the reponses the person did not make and setting it to 0.

I try it in a nested ForEach but get a Collection modified error.

Any ideas how to iterate over the keys of a hash table and insert new keys?


PS > $r=.\test.ps1

An error occurred while enumerating through a collection: Collection was
modified; enumeration operation may not execute..
At C:\PoSHScripts\Copy of NetMap\test.ps1:10 char:8
+ foreach <<<< ($key in $hash.keys) {

PS > $r

Name Value
---- -----
a {b, c}
b {c}

PS > $r.a

Name Value
---- -----
b 1
c 0

<Begin PowerShell>
$hash=@{}

$hash.a+=@{b=1}
$hash.b+=@{c=1}

$allItems=@{}
$allItems.b=1
$allItems.c=1

foreach($key in $hash.keys) {
foreach($item in $allItems.keys) {
if(-not ($hash.$key.keys -eq $item) ){
$hash.$key+=@{$item=0}
}
}
}

$hash
<End PowerShell>


<Begin Python>
# Fill in missing items with 0
for ratings in user_dict.values():
for item in all_items:
if item not in ratings:
ratings[item]=0.0
<End Python>