time series data truncating

i have a matlab table as:

time var1 var2 var3 var4

1/2/2019 04:10:11:234 10 100 Nan 15

1/2/2019 04:10:11:235 Nan Nan 5 Nan

1/2/2019 04:10:12:345 Nan 12 Nan 1

1/2/2019 04:10:12:346 1 Nan 4 Nan

And i want the final dataset as a 1 second sampled data like:

1/2/2019 04:10:11 10 100 5 15

1/2/2019 04:10:12 1 12 4 1

How do i implement this?

[Turlough Hughes]

Are you looking to round to the nearest second for the time data or emove the last 4 characters in the time string? It would be better to see a larger set of data, can you upload the table?