Hello
        I have a data consisting of 245 counties, including the population, 
number of illness and the geographical information of each county. Fixing each 
county, I want to sort the other county by distance, which can make a 245*245 
matrix with each cell is the corresponding index of the county, e.g. the 3rd 
row of the matrix is a vector of descending order of the 245 indices, maybe 
c(3,34,178,.....), means that the NO.34 county is the second closest the NO.3 
county.  We can call it DISTANCE matrix.
        From DISTANCE matrix, I can get a matrix POP and matrix CASE into the 
corresponding cell of the DISTANCE matrix respectively, by "cumsum" command and 
get matrix CUMPOP and matrix CUMCASE, which can explained different size circle 
of different center, and we can call a function element-wise 
        The problem, I want to restrict the cumulative population of each 
circle within 50% of the total population, which will make every row-vector 
have different length. e.g. the first row-vector have a length of 123, but the 
second maybe have a length of 141. I checked R_intro, it seems ragged array can 
do it, but I can't find any material to learn.
        1.Can anyone teach me how to creat and manage a matrix with vector of 
different length?
        2.Can anyone teach me 2 or 3 matrices call a function element wise by 
vectorization? e.g. for (i in 1:10) A[i]^B[i]/C[i]

        Thank you in advance                   

Yours sincerely
 



ZhaoXing
Department of Health Statistics
West China School of Public Health
Sichuan University
No.17 Section 3, South Renmin Road
Chengdu, Sichuan 610041
P.R.China          

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