[R] Axis whitout all the row, that contains time

[Informatique]

Hello,

i'm using Rstudio from a few day, and i have some information in a CVS file, take every five second, format of the time is HH:MM:SS.
I use the hour on the X axis, but i don't want having all the time print. For example only every 10 values.

I think it will be possible with   scale_x_datetime(breaks = date_breaks(XXX)

but i don't understand how select every 20 s.

Thank's for your help

François-marie BILLARD
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Informatique <informatique using billard-francois-marie.eu>