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expand.grid(i=rexp(5,rate=0.1)) It creates just one col but is there some way to multiply this easily to 5 cols? I mean the matlab-way-of-doing-things like rand('exp', 0.1, 10,20) (creating a matrix with exponentially-distributed-random-numbers with mean 0.1 of size 10x20), how?
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How to modify a matrix in R? We modify the R matrix by using the various indexing techniques along with the assignment operator. We can add a row or column by storing the new row/column in a vector and using the rbind() or cbind() functions to combine them with the matrix.
If we want to generate standard normal random numbers then rnorm function of R can be used but need to pass the mean = 0 and standard deviation = 1 inside this function.
To create a matrix in R you need to use the function called matrix(). The arguments to this matrix() are the set of elements in the vector. You have to pass how many numbers of rows and how many numbers of columns you want to have in your matrix. Note: By default, matrices are in column-wise order.
Use the matrix function:
matrix(rexp(200, rate=.1), ncol=20) ETA: If you want to do it without repeating the 200, you can define a function to do so:
fill.matrix = function(expr, nrow=1, ncol=1) { matrix(eval(expr, envir=list(x=nrow*ncol)), nrow=nrow, ncol=ncol) } fill.matrix(rexp(x, rate=.1), nrow=10, ncol=20) The x thus becomes the dummy variable you're talking about. Is that what you're looking for?
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you can do something like:
matrix(rexp(200), 10) And of course use what ever distribution you want.
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