use last valid value as imputation value, not last value from the block being imputed

[l-k-]

@vincentvanhees sorry, I should have noticed this yesterday. Currently a faulty block is being imputed with the last value from that same block. Is that correct? Should it maybe be imputed with the last valid value, which at that point is stored in rawAccel[1]?

[codecov-commenter]

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R/readAxivity.R	81.98% <66.66%> (ø)

[vincentvanhees]

Ok, whether the new block (rawAccel) is correct we will only know until the next block is is read as only then we will be able to check whether the block had an abnormal duration. So, maybe this is a lot harder to assess.

An alternative approach is to use one standard imputation c(0, 0, 1), and log all imputation events as we already do, and let user decide on a more appropriate imputation if they think that is relevant (edit: I mean that the user will have to do that outside the function with their own code).

[l-k-]

I definitely may be wrong because there's a lot going on, but I think the first element of rawAccel (rawAccel[1]) is coming from the block before prevRaw, so it's confirmed to be good.

When we get to the imputed values line, we have just read the new block (raw) and we determined that the previous block (prevRaw) is faulty. If prevRaw wasn't faulty, we would put it into rawAccel[2:rawLast,] . But rawAccel[1] has actually already been filled in by the last value of the block before prevRaw. That happened at the end of processing of the block before prevRaw, here