I am checking the input of a matrix is reciprocal in R, i.e. value on one side is = to 1/value..
So far I have..
AHP <- function(pairwisematrix){
## check the input data
if (!((is.matrix(pairwisematrix) || (is.data.frame(pairwisematrix)))))
stop("pairwise matrix must be a matrix or a data frame")
if (!(nrow(pairwisematrix) == ncol(pairwisematrix)))
stop("pairwise matrix must be a square matrix or a data frame")
for (i in 1:nrow(pairwisematrix)) {
for (j in 1:ncol(pairwisematrix)) {
if (i == j) { if (pairwisematrix[i,j] != 1) { stop("the central values in the reciprocal matrix must be 1.") }}
else { if ((pairwisematrix[i,j] == 1 / pairwisematrix[j,i]) || (pairwisematrix[j,i] == 1 / pairwisematrix[i,j])))) { stop("the pairwise matrix must be reciprocal (i.e. value on one side must = 1/value)") }}
}
}
out <- "all worked"
return(out)
}
but when I test:
check1 <- matrix(c(1,1/3,5,3,1,0.2,0.2,5,1),3,3,byrow=T)
test <- AHP(check1)
I get the error:
the pairwise matrix must be reciprocal (i.e. values on one side must =
1/value)0.333333 & 0.333333
I have tried converting the values to string, partial strings and tried identical(a,b,) with no success.
Does anyone have any ideas?
With many if s inside double for loops, I would be surprised if it works as intended.
R is designed for working with matrix, so you could write something like
AHP <- function(pairwisematrix){
if(!all(pairwisematrix == t(1/pairwisematrix)))
stop("the pairwise matrix must be reciprocal (i.e. value on one side must = 1/value)")
else
return("all worked")
}
AHP(check1)
#[1] "all worked"
Related
I am defining an S4 function class to ensure the length of the output equals the length of the input (sort of one-to-one, but not in the calculus sense), e.g.
EqLenOut <- setClass("EqLenOut", contains = "function")
.EqLenOut.validity <- function(object) {
msg <- NULL
if (length(formals(object)) > 1) {
msg <- c(msg, "EqLenOut must only have one argument.")
}
tst1 <- length(object(1:5)) != 5
tst2 <- length(object(1:6)) != 6
if (tst1 || tst2) {
msg <- c(msg, "EqLenOut output length must equal input length.")
}
msg
}
S4Vectors::setValidity2("EqLenOut", method = .EqLenOut.validity)
It works, but it is imperfect to test the function for two arbitrary numeric inputs. In my particular case, I will also be requiring numeric inputs & outputs. However, it would be nice to setup a general "equal-output" class that both equal output numeric or non-numeric functions could contain.
How to best (rigorously & efficiently) test if a function output length equals the input length, regardless of the input/output?
If there is a name for classes of functions that take an n-length input vector and return an n-length output vector, I would love to make the question title more specific.
I want write R code for Pythagoras theorem.
The Pythagorean Theorem states that the square of the hypotenuse (the side opposite the right angle) is equal to the sum of the squares of the other two sides.
(sideA)^2+(SideB)^2=hypotenuse^2
Now I wrote the R code as below:
pythag<-function(sidea,sideb){
if (sidea>=0&sideb>=0)
hypoteneuse=sqrt(sidea^2+sideb^2)
else if (sidea<0|sideb<0)
hypoteneuse<-"Values Need to be Positive"
else if (!is.vector(x))
hypoteneuse<-"I need numeric values to make this work"
print(hypoteneuse)
}
pythag(4,5)
pythag("A","B")
pythag(-4,-5)
In case of pythag(4,5) it is ok, also pythag(-4,-5) is giving comment "Values Need to be Positive".
But in case of pythag("A","B") I want comment "I need numeric values to make this work", but unfortunately my code does't work for this.
You can try like this:
get_hypotenuse_length <- function(height, base)
{
sides <- c(height, base)
if(any(sides < 0))
{
message("sides must be positive")
} else if(!is.numeric(x = sides))
{
message("sides can not be non-numeric")
} else
{
sqrt(x = sum(sides ^ 2))
}
}
Here's an annotated version. It is creating the function which takes the values a and b and calculates c. It is first testing if the values are numeric, if they are not numeric it will print your error message, otherwise it will ignore what is within those curly brackets and move on to the next test. The second test is checking that both are greater than zero (seeing as a triangle can't have a side of length zero or negative length). If it satifies the condition that both are >0 then it will calculate c, if not it will give the error stating that there are negative values.
# Feed it the values a and b (length of the two sides)
pythag <- function(a,b){
# Test that both are numeric - return error if either is not numeric
if(is.numeric(a) == FALSE | is.numeric(b) == FALSE){
return('I need numeric values to make this work')}
# Test that both are positive - return length of hypoteneuese if true...
if(a > 0 & b > 0){
return(sqrt((a^2)+(b^2)))
}else{
# ... give an error either is not positive
return('Values Need to be Positive')
}
}
Here's a more streamlined version:
pythag <- function(a,b){
if(is.numeric(a) == FALSE | is.numeric(b) == FALSE){return('I need numeric values to make this work')}
if(a > 0 & b > 0){return(sqrt((a^2)+(b^2)))}
else{return('Values Need to be Positive')}
}
And this is what it returns with your examples:
> pythag(4,5)
[1] 6.403124
> pythag("A","B")
[1] "I need numeric values to make this work"
> pythag(-4,-5)
[1] "Values Need to be Positive"
if x = c("sideA", "sideB"), then it will still be a vector so your test is.vector(x) will return true:
> is.vector(x)
[1] TRUE
But you want to test if it's numbers, so if it's numeric:
> is.numeric(x)
[1] FALSE
I have written a custom function that performs a mathematical transformation on a column of data with the inputs being the data and one other input (temperature). I would like to have 2 different logical checks. The first one is whether or not any values in the column exceed a certain threshold, because the transformation is different above and below the threshold. The second is a check if the temperature input is above a certain value and in that case, to deliver a warning that values above the threshold are unusual and to check the data.
Right now, I have the function written with a series of if/else statements. However, this a warning that it is only using the first element of the string of T/F statements. A simplified example of my function is as follows:
myfun = function(temp,data) {
if(temp > 34){
warning('Temperature higher than expected')
}
if (data > 50) {
result = temp*data
return(result)
} else if(data <= 50) {
result = temp/data
return(result)
}
}
myfun(temp = c(25,45,23,19,10), data = c(30,40,NA,50,10))
As you can see, because it is only using the first value for the if/else statements, it does not properly calculate the return values because it doesn't switch between the two versions of the transformation. Additionally, it's only checking if the first temp value is above the threshold. How can I get it to properly apply the logical check to every value and not just the first?
-edit-simplified the function per #The_Questioner's suggestion and changed < 50 to <= 50.
The main issue with your code is that you are passing all the values to the functions as vectors, but then are doing single element comparisons. You need to either pass the elements one by one to the function, or put some kind of vectorized comparison or for loop into your function. Below is the for loop approach, which is probably the least elegant way to do this, but at least it's easy to understand what's going on.
Another issue is that NA's apparently need to be handled in the data vector before passing to any of your conditional statements, or you'll get an error.
A final issue is what to do when data = 50. Right now you have conditional tests for greater or less than 50, but as you can see, the 4th point in data is 50, so right now you get an NA.
myfun = function(temp,data) {
result <- rep(NA,length(temp))
for (t in 1:length(temp)) {
if(temp[t] > 34) {
warning('Temperature higher than expected')
if (!is.na(data[t])) {
if (data [t] > 50) {
result[t] <- temp[t]*data[t]
} else if(data[t] < 50) {
result[t] <- temp[t]/data[t]
}
}
} else {
if (!is.na(data[t])) {
if (data[t] > 50) {
result[t] <- temp[t]*data[t]
} else if(data[t] < 50) {
result[t] <- temp[t]/data[t]
}
}
}
}
return(result)
}
Output:
> myfun(temp = c(25,45,23,19,10), data = c(30,40,NA,50,10))
[1] 0.8333333 1.1250000 NA NA 1.0000000
I made a function to to compute the sum of I(Xi
my.ecdf<- function(x,y) {
if(!is.null(dim(y)))
stop("y has more than one dimension")
n<-length(x)
i<-1:n
p<-if(x[i]<y) 1 else {
0
}
(sum(p))/n
}
But when I run it with input (rnorm(11),6), I get this error:
Warning message:
In if (x[i] < y) 1 else { :
the condition has length > 1 and only the first element will be used
Any ideas? I'm new to r so sorry if it's something obvious. (Also I don't want to use the for loop)
There are a number of issues in your code:
1) Whats the point of x[1:length(x)] in the if statement? Right now these are meaningless and can be dropped:
n<-length(x)
i<-1:n
x[i]
2) If statement accepts a logical argument not a vector of logical, you can consider adding all() any() etc like
if(all(x < y)) 1 else {0}
or use ifelse() statement for the assignment
3) Finally from what I can understand you overcomplicate things and the whole thing can be written as one-liner:
sum(x < y)/length(x)
This is a logical vector of the same length as y
is.null(dim(y))
You're using it as a logical test. An object with a length greater than 1 can't be unambiguously interpreted by the if statement. Consider if (TRUE FALSE FALSE TRUE) <do something>. When should you do that thing?
If you want to make sure y doesn't have more than one dimension, do
if(length(dim(y)) > 1){
stop("message")
}
I did some programming work on R language to do the bubble sort. Sometimes it works perfectly without any error message, but sometimes, it shows "Error in if (x[i] > x[i + 1]) { : argument is of length zero". Can any one help me check whats wrong with it? I have attached my code below
example <- function(x) {
n <- length(x)
repeat {
hasChanged <- FALSE
n <- n - 1
for(i in 1:n) {
if ( x[i] > x[i+1] ) {
temp <- x[i]
x[i] <- x[i+1]
x[i+1] <- temp
hasChanged <- TRUE
cat("The current Vector is", x ,"\n")
}
}
if ( !hasChanged ) break;
}
}
x <-sample(1:10,5)
cat("The original Vector is", x ,"\n")
example(x)
The error occurs because you are iteratively decreasing n. Depending on the original vector's order (or lack thereof), n can reach the value of 1 after the last change. In that case, a further reduction of n in the next iteration step addresses the value x[0], which is undefined.
With a minimal correction your code will work properly, without giving error messages. Try to replace the line
if ( !hasChanged ) break;
with
if ( !hasChanged | n==1 ) break
Basically you have two termination criteria: Either nothing has been changed in the previous iteration or n is equal to one. In both cases, a further iteration won't change the vector since it is already ordered.
By the way, in R programming you don't need a semicolon at the end of a command. It is tolerated/ignored by the interpreter, but it clutters the code and is not considered good programming style.
Hope this helps.