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Katia Bobulova asked three questions. My answers below.
Nick
[email protected]
I have some problems in managing my dataset. I have a dataset with
high frequency data, with observations about time, date, price,
quantity and a code for the type of security.
Question 1
==========
I have the time in this format: 63000 and i want to construct a
"timedate" variable, which contains both the data and the time.
First af all I tried to modify the format of the time typing:
g hours=int(time/10000)
g minutes=int((time-hours*10000)/100)
g seconds=int(time-hours*10000-minutes*100)
g newtime=hms(hours, minutes, seconds)
format newtime%tc
However, after typing hms() I receive this message:
Unknown function hms()
r(133);
The next step would be typing something like:
gen double timedate=date*24*60*60*1000+time
format timedate %tcNN/DD/CCYY_HH:MM:SS
Answer 1
========
-hms()- is an -egen- function written by Kit Baum and is included in the
-egenmore- package from SSC. It will _only_ work with -egen-, not with
-generate-.
But you don't need it. You did almost all the work yourself.
Assuming that e.g. 63000 is 06:30:00 then given your variables -hours-,
-minutes-, -seconds-,
gen long time_in_sec = 3600 * hours + 60 * minutes + seconds
Question 2
==========
I have two types of prices: price1 and price2. I would like to
create a variable which takes the difference between the lowest value
of price1 and the highest value of price2 for each data and time.
First of all I sorted my dataset:
sort date time price1 price2
then I generated the new variable:
gen price3=(price1[_n]-price2[_N] & date==(26feb2008) & time==63000
But as a result I have all missing values, furthermore I have to do
this for each date and time, so i was wondering if there is a way to
instruct Stata to create this new variable for each time and data.
Answer 2
========
I don't understand how you reached your solution, nor why it produces
missing values.
I don't think your -sort- order guarantees what you want, but it looks
quite wrong any way.
This is likely to be closer to where you want to be.
bysort date time (price1) : gen diff = price1[1]
bysort date time (price2) : replace diff = price2[_N] - diff
Question 3
==========
I have to divide my variable time in equal time intervals. For
example, i have observations at 14:41:38 and 15:28:32 and I would like
to have observations at precise time intervals, for example each
5-minute, i.e. at 14:40:00, 14:45:00 and so on. Any idea on how to do
this?
Answer 3
========
Create another dataset with regularly spaced observations and then
-merge-.
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