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# Re: st: Going through each observation of a variable

 From David Kantor To statalist@hsphsun2.harvard.edu Subject Re: st: Going through each observation of a variable Date Sat, 08 Jun 2013 17:44:00 -0400

```Hello Derya,
See below.

At 02:52 PM 6/8/2013, you wrote:
```
```Hi David,

```
Organization of the data is that I simply copy-pasted these prices in the data as additional variables. The variables Price1 and Price2 has 500 observations, each row representing a price vector. os1 and os2 are the expenditure shares for each individual and has 80,000 observations.
```
```
I am computing Y for each individual as the expenditure share of good1 for each individual (os1), multiplied by price of good 1 (P1) plus the same for good 2. If I had only a single price vector, this is straightforward to compute. I could just write 'genY=os1*P1+os2*P2'. But I have 500 different price vectors. I would like to generate Y 500 times, and take the average across the 500.
```
```
The program I posted choose randomly from these price vectors. But I don't want randomness at this stage. I would like to compute Y for each price vector one by one...This is what I meant by replication.
```
```
Here is an example with 3 price vectors and 10 individuals to show what I am trying to do: https://www.dropbox.com/s/boslxhpkyljcq45/Book1.xlsx
```
Thanks again, greatly appreciated!

Derya
[...]
```
```
It seems that you have two datasets:
1, prices: 500 observations
2, individuals: 80000 obsrvations

Or that in some virtual sense, this is what you have.
But it's still not clear how you have it organized.
```
Are all these observations packed into one dataset? Is it that they are together -- stacked on top of each other, then it is a meaningless "structure". On the other hand, maybe you need a cross-product of the two datasets; maybe it is already in that form; it would have 40000000 observations. That's a lot of data -- and redundant. but it might be the right shape to do the job. If it's not already in that shape, then you can combine them with -cross-.
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But again, that's a lot of observations. Your system might choke.
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I would guess that your main dataset if the individuals, and each individual needs to be mated with the prices data.
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```
It may be better to store the prices data in a matrix or a virtual matrix using macros. Maybe that's what you have in mind. It may be a situation that works well in Mata, but I am no expert in that.
```
Other options:
create wide data; still a lot of data.
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step through each individual grabbing one at a time; cross that with the prices, and output the result (or write it to a Stata data file).
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```
We can best proceed if you clarify how each of these two datasets are stored -- and if they are together, how.
```--David

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