I'm trying to use if function to create a vector X that follows the pattern of the if statement, that is length 5. However, when I print X, I get 5 vectors with length 1. How do I fix this
for (i in 1:5) {
if (i <2){
a<-i
}
else {
a<-(i-1)
}
X<-a
print(X)
}
R overwrites the contents of your variables a and X with each loop. To avoid this, you can make X a list, and put your value in a different position with each loop.
X <- list()
a <- list()
for(i in 1:5) {
if(i<2){
a <- i
} else {
a <- i-1
}
X[i] <- a
}
Since your final plan is to create a vector, you may initialize a vector ("X") first, and then add a value ("a") in each 'for' loop.
X = vector("numeric",0)
for (i in 1:5){
if (i<2){
a <- i
}
else{
a <- (i-1)
}
X = c(X, a)
print(X)
}
X
# [1] 1 1 2 3 4
Related
i'm having trouble printing out the names in the for loop. This is what I have. I'm trying to print the names of the passengers who are the ages of less or equal to 14.
x <- c()
for(i in length(titanicDataset$name)){
if(titanicDataset$age[i] <= 14){
x[i] <- titanicDataset$name[i]
}
}
print(x)
it just prints NULL
length returns a single value. Instead, it should be 1:length or seq_along
x <- character(nrow(titanicDataset))
for(i in seq_along(titanicDataset$name)) {
if(titanicDataset$age[i] <= 14){
x[i] <- titanicDataset$name[i]
}
}
We don't need a loop for this as these are vectorized
with(titanicDataset, name[age <= 14])
You have to specify then range for loop (1:length(...)),
and concatenate new data to x:
x <- c()
for(i in 1:length(titanicDataset$name)){
if(titanicDataset$age[i] <= 14){
x <- c(x, titanicDataset$name[i])
}
}
print(x)
For the next exercise: From a certain numerical value, check if this is a natural number or not so that, if it is, it shows the divisors of this number and, if it is not, it shows an error message.
As there was no predefined function for this I wrote:
n <- 102
x <- n
res <- c()
while (x>0){
if (n%%x == 0){
res[x] <- x
x = x-1
} else {
x = x -1
} print("The values are ", res)
}
res
Works nice, except it´s not storing the values inside the vector. Any ideas?
I´m new to programming and stackoverflow. I hope this question is right posted and presented.
Cheers
What you need is a counter "i" to save the value in the next entry of the vector
n <- 102
x <- n
res <- c()
i<-1
while (x>0){
if (n%%x == 0){
res[i] <- x
x = x-1
i<-i+1
} else {
x = x -1
}
}
res
I want to create a function that returns its result as a vector. More specifically, a function that returns the divisors of an input value and places them inside a vector.
divisors<-function(n){
i <- 2
c<-1
x<-c()
while(i <= n) {
if(n%%i==0) {
x[c]<-i
}
i <- i + 1
c<-c+1
x
}
}
I edited a bit your code in order to return a vector and avoid NA values.
divisors <- function(n){
i <- 2
x<-vector("integer")
while(i <= n) {
if(n%%i == 0) {
x <- c(x, i)
}
i <- i + 1
}
x
}
I created a function with that I want to calculate (several) vectors of data.
Actually the vctors should be for a range (1:100) for one variable while the others stay constant at differnt values in turn.
The function is:EI <- function(x,y,z) {(x+y)/(2*(2*x+y)+z)}
my Problem is, the sum of x+y+z has to be limited to 100. And i don't know how to tell it the function.
For example, if x = 20, y can only take values from 0:80 , i.e. (100-20), and z can takey values from 0 : 100-(x+y).
I used the following code where z is not regarded all. I thought, I would get at least one large vector, but all I get is a single number:
for(x in 1:100) {
for(y in 0:(100-x)) {
for(z in 0:(100-(x+y))) {
v1 <- c(EI(x,y,z))
}
}
}
I need to tell the function EI() that the sum of x+y+z has alwys to be 100.
Has anybody an idea how to solve this problem?
If you want to create a vector you need to do that:
v1 <- c()
for(x in 1:100) {
for(y in 0:(100-x)) {
for(z in 0:(100-(x+y))) {
v1 <- c(v1, EI(x,y,z))
}
}
}
Unfortunately this will be slow (because at each step you are reallocating a new vector), a better alternative is to begin by allocate your vector with the appropriate size:
v1 <- numeric(171700)
k <- 0
for(x in 1:100) {
for(y in 0:(100-x)) {
for(z in 0:(100-(x+y))) {
k <- k + 1
v1[k] <- EI(x,y,z)
}
}
}
You can also write the same thing with sapply function and this is slightly faster:
v1 <- unlist(sapply(1:100,
function(x) {
unlist(sapply(0:(100-x),
function(y) {
sapply(0:(100-(x+y)),
function(z) {EI(x,y,z)}) }))}))
I am new to writing loop functions and I am trying to solve this. I would like the y matrix to be populated with the values obtained from the for loop. Unfortunately y remains blank and full of 0's after the loop is executed.
mv <- c(0,1,2) # location vector
s <- 1 # scale
increment <- seq(-6,6,0.01) # Create a sequence of x values
y=matrix(0,length(increment),length(mv))
for (i in length(increment)) {
for (j in length(mv)) {
y[i,j] <- 1/(1+ exp(-(increment[i]-mv[j])/s))
}
}
Change your loop to start at 1, for now it is only using 1 value (length(increment)):
for (i in 1:length(increment)) {
for (j in 1:length(mv)) {
y[i,j] <- 1/(1+ exp(-(increment[i]-mv[j])/s))
}
}