Filling matrix with data from two columns of dataframe

Question

I am so desperated and even I am ready to lose some more rep points but I have to ask it. (Yes, I read some threads about it).

I created a dataframe with only 2 columns I want to put to the matrix (I didn't know how to pick just 2 columns from whole data):

    tbl_corel <- tbl_end[,c("diff", "abund_mean")]

In next step I created and empty matrix:

## Creating a empty matrix to check the correlation between diff and abund_mean
mat_corel <- matrix(0, ncol = 2)
colnames(mat_corel) <- c("diff", "abund_mean")

I tried to use that function to fill the matrix with the data:

mat_corel <- matrix(tbl_corel), nrow = 676,ncol = 2)

Of course I had to check manually how many rows I have in my data frame... It doesn't work. Tried that function as well:

mat_corel[ as.matrix(tbl_corel) ] <- 1

It doesn't work. I'd be so grateful for the help.

  diff abund_mean
1    0 3444804.80
2    0  847887.02
3    0   93654.19
4    0  721692.76
5    0  382711.04
6    1  428656.66

I'm unsure what you're trying to do here. You can check the correlation of 2 columns of your data frame in the data frame itself by specifying either the column names or the column indices to the cor() function. — ydaetskcoR
– ydaetskcoR, Commented Oct 17, 2013 at 10:06

juba · Accepted Answer · 2013-10-17 10:07:28Z

6

If you want to create a matrix from your two-columns data frame, there is a more direct and simpler way : just transform you data frame as a matrix directly :

mat_corel <- as.matrix(tbl_corel)

But if you just want to compute a correlation coefficient, you can do it directly from your data frame :

cor(tbl_end$diff, tbl_end$abund_mean)

answered Oct 17, 2013 at 10:07

juba

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6 Comments

Shaxi Liver Over a year ago

Thanks, that's so easy to do if you ask someone. That's what I wanted. I tried "mat_corel <- matrix(tbl_corel)". Forgot about "as". I wish I could vote up your answer. Thx once again.

juba Over a year ago

Not asking for rep, but do you know that even if you can't upvote an answer, you can accept it by checking the green mark on its left ? This allows for visitors to know at a glance that the question had been answered.

Shaxi Liver Over a year ago

Already did. Trying now to plot my results using: "pdf(file="myplot.pdf", width = 10, height =13) #create new pdf plot(diff ~ abund_mean) #see data but got this problem "Error in (function (formula, data = NULL, subset = NULL, na.action = na.fail, : object is not a matrix"

juba Over a year ago

Use plot(diff~abund_mean, data=tbl_end). But please don't ask questions in a comment, Open a new question if you really ned it.

Shaxi Liver Over a year ago

Okey, in future I will make another question. I was just worried about my rep.

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