Dear R users,
Consider the first two columns of a data frame like this:
> z[,1:2]
x y
1 1 1
2 2 2
3 3 3
4 1 4
Imagine that y represents the times that the value x happens in a population.
But z is not exactly a frequency table, because in z we have x=1 twice. So, the
x=1 in the first line and the x=1 in the fourth are not the same, differing
according to a third variable in the data frame.
Now, I use the function rep() in order to obtain a vector of values of x in the
population:
> x.pop <- rep(x,y)
> x.pop
[1] 1 2 2 3 3 3 1 1 1 1
How can I go from x.pop back to z? If I use table(x.pop), I obtain a frequency
table like the one below, but not z.
> table(x.pop)
x.pop
1 2 3
5 2 3
(I know I haven't deleted z, obviously, but I need to write a piece of code to
do something very similar).
Just in case anyone is wondering by now whether this is an assignment for
college, etc.,-it is not. The real world problem I'm working on at the moment
has to do with income distribution in Northern Ireland. I want to see how many
people would leave poverty if the income of those currently below 60% median
income increases by, say, £20 a week. I am working with the Family Resources
Survey sample for Northern Ireland (n=2,263), which I have to gross up before
increasing the incomes (grossed up n=1,712,886). Once I increased the income
figures for those individuals in poverty, I need to 'un-gross' the data to get
back to n=2,263 -and table() simply does not do the trick, because of exactly
the same situation in the example above.
So, please, how can I retrieve z?
Many thanks,
Jose
Mr José Luis Iparraguirre
Senior Research Economist
Economic Research Institute of Northern Ireland
2 -14 East Bridge Street
Belfast BT1 3NQ
Northern Ireland
United Kingdom
Tel: +44 (0)28 9072 7365
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