urgent: question concerning data manipulation

Hello everyone!

Does anyone of you know how I could solve the following problem.
I guess, it is not a very difficult question, but I simply lack of the
right idea:

I have a dataset containing data of convictions. This dataset contains 4
columns:
- personId: individual number that identifies the offender
- law: law which has been violated
- article: article which has been violated

# Testdata:
personId<-c(1,1,2,2,2,2,2,3,4,4)
law<-c("SVG", "SVG", "StGB", "StGB", "SVG", "AuG", "StGB", "SVG", "StGB",
"AuG")
article<-c(10, 10, 123, 122, 10, 40, 126, 10, 111, 40)
testdata<-data.frame(personId, law, article)

Now I'd like to create three additional dummy-coded columns for each law
(SVG, StGB, AuG).
For each offender (all offenders have the same personId) it should be
checked, whether there are
any violations against the three laws. If there are any violations against
SVG (for example), then
in all rows of this offender the column SVG should have the value 1
(otherwise 0).

For example offender 2 has once violated against law "SVG" therefore his
four entries should have
the value 1 at the column "SVG".

I hope you can understand my problem. I'd really appreciate any hints and
solutions!

Thank you!
David

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