[R] Select rows from Data Frame with conditions

[Jeff Newmiller]

Something along the lines of

top100 <- A[match(B,A[,1]),]

Please provide R code with sample data and desired output. See http://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example
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Sent from my phone. Please excuse my brevity.

Sachinthaka Abeywardana <sachin.abeywardana at gmail.com> wrote:

>Hi all,
>
>I have two dataframes. The first (A) contains all the stock prices for
>today including today. So the first column is the stock Symbol and the
>second column is the stock price. The second (B) is the symbol list in
>the
>top 100 stocks.
>
>I want to pick out from dataframe A only the rows containing the
>symbols
>from B. i.e. something like:
>
>            prices <- A[A[,1]==B,2]
>
>is there any way to do this without using a for loop, I have to do this
>365
>times (i.e. for one year).
>
>Thanks,
>Sachin
>
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>
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