Hi When I put together my solution to create the graph and then also tried the exact notation given in the solutions I do not get the same graph as in the solutions. Can you confirm this is definitely correct? I have checked and re-checked my work but cannot see that I have done anything different to the solutions, but still end up with a different graph. Many thanks. Rachael
Hello I believe it's correct. It's hard to check your solution without any code, can you provide your script? At a guess you may be having an issue with where your minus signs are in the function. For example, the below function works: logL <- function(x){ 18*x-4*log(30*exp(x)+17)-4*log(27*exp(x)+14)-log(23*exp(x)+14)- 2*log(22*exp(x)+12)-2*log(20*exp(x)+10)-5*log(18*exp(x)+8)- 2*log(12*exp(x)+8)-log(10*exp(x)+8)-2*log(7*exp(x)+4)} I've highlighted the minus signs at the end of the line - this tells R that the expression is not over and to continue to the next line. The below function does not work: logL <- function(x){ 18*x-4*log(30*exp(x)+17)-4*log(27*exp(x)+14)-log(23*exp(x)+14) -2*log(22*exp(x)+12)-2*log(20*exp(x)+10)-5*log(18*exp(x)+8) -2*log(12*exp(x)+8)-log(10*exp(x)+8)-2*log(7*exp(x)+4)} Here, R calculates three separate numbers as it does not treat it as one long expression. The way functions work is they return the last number calculated, so this is just returning -2*log(12*exp(x)+8)-log(10*exp(x)+8)-2*log(7*exp(x)+4) and not the full expression. A slightly simpler example is as follows: my.function = function(x){ x- 4 } my.function(3) [1] -1 my.function2 = function(x){ x -4 } my.function2(3) [1] -4 my.function(3) returns 3-4 = -1. my.function2(3) returns -4 (effectively ignoring the input) as this is the last calculation line in the function. Hope this helps Andy
