Hi,
I have an excel data table that looks like this (file attached):
Test | Signal 1 | Signal 2 | Signal 3 |
1 | 3 | 3 | 4 |
2 | 4 | not reached | |
3 | 5 | | 6 |
4 | 6 | | not reached |
It includes a number of tests. Each test has a number of signal channels (Signal 1-3), but not all channels were used for all tests. In cases where the signal channel was not used for a given test the corresponding field is empty.
The numerical values for each channel mark the time when the signal reaches a certain threshold value. If the signal does not reach the threshold, this in indicated by the string "not reached".
For the evaluation it would be important to be able to distinguish between the two cases of missing data:
1) there is no data because the channel was not used.
2) there is no data because the threshold was not reached.
Currently the data are all of type "character" but of course I need to convert them into "numeric" for the evaluation. However, as soon as I convert the data type of a column to "numeric" the entries "not reached" are deleted and there is no distinction anymore between the two types of missing data.
I've tried to use the recode option to replace "not reached" by NaN or nan and then convert the columns to numeric but the result was the same (the NaN or nan were deleted).
Is there a way that would allow distinguishing between the two cases of missing data? I thought of having no value in one case and something like NaN in the other case.
(Either an interactive or a scripting solution would be fine.)