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RE: st: dot product across many variables
From
Nick Cox <[email protected]>
To
"'[email protected]'" <[email protected]>
Subject
RE: st: dot product across many variables
Date
Tue, 29 Nov 2011 18:16:17 +0000
Talking of which,
. edit
. set obs 10
obs was 0, now 10
. forval i = 1/3 {
2. gen first`i' = runiform() > `i' * 0.2
3. gen second`i' = runiform() < `i' * 0.2
4. }
. l
+--------------------------------------------------------+
| first1 second1 first2 second2 first3 second3 |
|--------------------------------------------------------|
1. | 0 0 0 0 1 1 |
2. | 1 1 0 0 0 0 |
3. | 1 0 1 1 0 1 |
4. | 1 0 1 1 0 1 |
5. | 1 0 1 0 1 1 |
|--------------------------------------------------------|
6. | 0 0 1 1 0 1 |
7. | 1 0 1 0 0 1 |
8. | 0 0 1 1 1 1 |
9. | 1 0 0 0 0 1 |
10. | 1 0 1 1 1 0 |
+--------------------------------------------------------+
. mata
------------------------------------------------- mata (type end to exit) --------------------------------------------------------------------
: x = st_data(., "first1 first2 first3")
: y = st_data(., "second1 second2 second3")
: x :* y
1 2 3
+-------------+
1 | 0 0 1 |
2 | 1 0 0 |
3 | 0 1 0 |
4 | 0 1 0 |
5 | 0 0 1 |
6 | 0 1 0 |
7 | 0 0 0 |
8 | 0 1 1 |
9 | 0 0 0 |
10 | 0 1 0 |
+-------------+
: rowsum(x :* y)
1
+-----+
1 | 1 |
2 | 1 |
3 | 1 |
4 | 1 |
5 | 1 |
6 | 1 |
7 | 0 |
8 | 2 |
9 | 0 |
10 | 1 |
+-----+
Nick
[email protected]
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Paul Burkander
Sent: 29 November 2011 18:12
To: [email protected]
Subject: Re: st: dot product across many variables
ah, that's great. Much better than having to learn mata in day.
Thanks!
On Tue, Nov 29, 2011 at 1:03 PM, Nick Cox <[email protected]> wrote:
> Consider a loop
>
> gen newdummy = 0
>
> forval j = 2000/2010 {
> replace newdummy = newdummy + firstdummy`j' * seconddummy`j'
> }
>
> On Tue, Nov 29, 2011 at 5:11 PM, Paul Burkander <[email protected]> wrote:
>
>> I have a data set that has two binary variables in each of several
>> years. I'd like to create a new variable that is the sum across all
>> years of the product of the two within year.
>>
>> For example,
>> firstdummy2000=1
>> seconddummy2000=0
>> firstdummy2001=1
>> seconddummy2001=1
>>
>> newdummy=(firstdummy2000*seconddummy2000+firstdummy2001*seconddummy2001)=1
>>
>> There are so many years that it seems cumbersome to do it as above,
>> moreover the years might change over time and I'd like to be flexible.
>>
>> I thought perhaps a matrix command would work, doing a dot product?
>>
>
> *
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*
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*
* For searches and help try:
* http://www.stata.com/help.cgi?search
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/