Generating a variable that reflect the same responses while ignoring missing values

[imane imane]

Hi everyone,

I have a dataset with travel modes used in trips by individuals. The number of observations varies beween individuals. Also, not all the travel modes are informed (so i have for every individual some missing values). I need to know the individuals that did not change their travel mode between the different trips.

The variables I use are:
ID: individuals
Ndep: the trip code (starting from 1)
mode: used mode (variable with missing values)

I tried the command:
by ID, sort : gen same= mode[1]==mode[_N]

But STATA do not ignore the missing values. So it considers that for an individual, an observation with a missing value is different than the others, even if the other observations have the same value.

How to tell STATA to ignore the missing values?

Thanks

[George Ford]

The gen command appears only to compare the first and last case within ID. Is that what you want, or do you want a run?

I'd dataex some data. You'll get more and better help that way. (And please post some interesting data that reveals your problem).

[imane imane]

Thank you for your answer,

I want to compare all the cases per individual, if they are the same while ignoring the missing values.

here an example

ID_bis ndep mode
1 1 .
1 2 3
1 3 .
1 4 3
1 5 .
1 6 .
2 1 2
2 2 3
2 3 .
2 4 3
3 1 3
3 2 3
4 1 1
4 2 1
4 3 1
4 4 1
4 5 1
4 6 1
4 7 .
4 8 .
4 9 1
4 10 1
4 11 1

The 1st indidividual used only the mode 3, while the 2nd used different modes (2 and 3).

I want to know the individuals that only use one particular mode in all their trips

[George Ford]

ssc install egenmore

egen temp = nvals(mode) , by(id_bis)
egen modecount = max(temp), by(id_bis)
drop temp

[imane imane]

Thank you George