Hello R users, I have been looking through Help files and Nabble list for the answers for these simple questions, but it seems to be fruitless. 1- in a data frame with two columns, x and y, how do I get the corresponding value of x to, let's say, the minimum value of the y column (min (data$y)) ? 2- how do I solve a simple equation? Considering the equation y= exp(-x)^12, I would like to find the values of x for, for example, y=0.01, so exp(-x)^12=0.01. How do I do that using R? I know those a probably very, very simple questions, but for which I do not seem to find the answer. Thank you very much, Marcia -- View this message in context: http://www.nabble.com/simple-problems-tf4958407.html#a14200401 Sent from the R help mailing list archive at Nabble.com.
marciarr wrote:> Hello R users, > I have been looking through Help files and Nabble list for the answers for > these simple questions, but it seems to be fruitless. > 1- in a data frame with two columns, x and y, how do I get the corresponding > value of x to, let's say, the minimum value of the y column (min (data$y)) ? >data$x2[data$x1==min(data$x1)]> 2- how do I solve a simple equation? Considering the equation y= exp(-x)^12, > I would like to find the values of x for, for example, y=0.01, so > exp(-x)^12=0.01. How do I do that using R? >I know there is solve for linear equations, but I do not know if there is a generic solver for other equations. You could implement it using a numerical approach (perhaps it is yet in some package). domenico
On Dec 6, 2007 3:26 PM, marciarr <marcia.rocha at gmail.com> wrote:> > Hello R users, > I have been looking through Help files and Nabble list for the answers for > these simple questions, but it seems to be fruitless. > 1- in a data frame with two columns, x and y, how do I get the corresponding > value of x to, let's say, the minimum value of the y column (min (data$y)) ?In the builtin Formaldehyde data frame find the value of carb (first column) which corresponds to the least value of optden (second column): with(Formaldehyde, carb[which.min(optden)])> 2- how do I solve a simple equation? Considering the equation y= exp(-x)^12, > I would like to find the values of x for, for example, y=0.01, so > exp(-x)^12=0.01. How do I do that using R? > I know those a probably very, very simple questions, but for which I do not > seem to find the answer.Search between 0 and 1 for the root of the indicated function: uniroot(function(x) 0.1 - exp(-x)^12, 0:1)