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POR: relative frequency in r by factor
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  1. POR: relative frequency in r by factor
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    copied!<p>I would like to get a table of top 10 absolute and relative frequencies for a variable across other factor variable. I have a dataframe with 3 columns: 1 column is a factor variable, 2nd is other variable I need to count, 3 is logical variable as a constraint. (real database has more than 4mln observations)</p> <pre><code>dtf&lt;-data.frame(c("a","a","b","c","b"),c("aaa","bbb","aaa","aaa","bbb"),c(TRUE,FALSE,TRUE,TRUE,TRUE)) colnames(dtf)&lt;-c("factor","var","log") dtf factor var log 1 a aaa TRUE 2 a bbb FALSE 3 b aaa TRUE 4 c aaa TRUE 5 b bbb TRUE </code></pre> <p>So I need to find top absolute and relative frequencies of "var" where "log"==TRUE across each factor of "factor".</p> <p>I've tried this with absolute frequencies (in real db I extract top 10, here I get 2 lines):</p> <pre><code>t1&lt;-tapply(dtf$var[dtf$log==T],dtf$factor[dtf$log==T],function(x)(head(sort(table(x),decreasing=T),n=2L))) # Returns array of lists: list of factors containing list of top frequencies t2&lt;-(t1, ldply) # Split list inside by id and freq t3&lt;-do.call(rbind, lapply(t2, data.frame)) # Returns dataframe of top "var" values and corresponding freq for each group in "factor" # Factor variable's labels are saved as row.names in t3 </code></pre> <p>The following function helps to find relative frequency as for the whole database, not grouped by factors:</p> <pre><code>getrelfreq&lt;-function(x){ v&lt;-table(x) v_rel&lt;-v/nrow(dtf[dtf$log==T,]) head(sort(v_rel,decreasing=T),n=2L)} </code></pre> <p>But I have problems with relative frequencies as I need to divide the absolute frequency by number of rows of "var" BY EACH factor, not TOTAL nrow of "var" where "log"==T. I don't know how to use that in tapply loop such that the denominator will be different for each factor. I also would like to use both functions in 1 tapply loop instead of generating many tables and merging results. But have no idea how to put such 2 functions together.</p> <p>Help please :)</p>
 

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