First post ever, excuse my ignorance as I'm relatively new to programming. I'm trying to create a function that samples a number given by x and returns "number too small" below 5 and "number too big" if its above 10. I already figured this part out, however my issue is that I want to add an optional len argument that will display the length of x if used and if not will still function as intended. I'm sure its possible if I just do a bunch of if else statements with every possible scenario, but is there a more organized way to achieve my goal. Was thinking that I can make another if/else that returns null if they opt out of the second len argument but unsure on how i would code it as I already have two if or else statements.
vector.maker.num2 <-function(x){
generator <-sample(1:20, x)
if (x < 5) {
print(c(generator, "warning, number too low"))
}
if (x > 10) {
print(c(generator, "warning, number too high"))
}
}
vector.maker.num2(4)
It sounds like what you want is the missing function.
vector.maker.num2 <-function(x, len){
generator <-sample(1:20, x)
if (!missing(len)) {
print(length(x))#Will usually print 1, because x is a vector of length 1.
}
if (x < 5) {
print(c(generator, "warning, number too low"))
}
if (x > 10) {
print(c(generator, "warning, number too high"))
}
}
vector.maker.num2(4)
Related
I am trying to define a function with a for loop and inside a conditional in R studio. Yesterday I was able with the help of another thread to devise this piece of code. The problem is that I want to sum the vector elements ma for any possible x, so that is inside the function l. This is a simpler case which I am trying to solve to adapt the original model. However, I do not know how to proceed.
ma<-rep(0,20)
l <- function(x, ma) {
for(i in seq_along(ma)) {
if(i %% 2 == 1) {
ma[i] <- i + x
} else {
ma[i] <- 0
}
}
return(ma)
}
My problem is that I would like to have the sum of i+x+0+i+x... for any possible x. I mean a function of the kind for any possible x.
Question:
Can someone explain to me how to implement such a function in R?
Thanks in advance!
I am going to update the original function:
Theta_alpha_s<-function(s,alpha,t,Basis){
for (i in seq_along(Basis)){
if(i%% 2==1) {Basis[i]=s*i^{-alpha-0.5}*sqrt(2)*cos(2*pi*i*t)}
else{Basis[i]=s*i^{-alpha-0.5}*sqrt(2)*sin(2*pi*i*t)}
}
return(Basis)
}
If you don't want to change the values in Basis, you can create a new vector in the function (here result) that you will return:
l = function(s,alpha,t,Basis){
is.odd = which(Basis %% 2 == 1)
not.odd = which(Basis %% 2 == 0)
result = rep(NA, length(Basis))
result[is.odd] = s*is.odd^{-alpha-0.5}*sqrt(2)*cos(2*pi*is.odd*t)
result[not.odd] = s*not.odd^{-alpha-0.5}*sqrt(2)*sin(2*pi*not.odd*t)
#return(result)
return(c(sum(result[is.odd]), sum(result[not.odd])))
}
I am new to R and I am having difficulty with a simple recursion function. I initialize a variable, x to .1 and then make a call to a recursive function in which if x is not equal to the user-input number, it will add .1 to x and recursively call the function again. If x is greater than the input number, the function returns an error message.
I have tried setting x to a whole number, mainly 1 and then trying to evaluate the function. This process works, so I figure that there is an issue of adding decimal numbers to each other and then evaluating their equality with a whole number.
u<-function(a)
{
#Initialize r
x<-.1
#Call to recursive method
v(a, x)
}
#Recursive function
v<-function(a, x)
{
#Check for current value of a and r
print(a)
print(x)
if(a==x) {
return("Yes")
}
else if(a < x) {
return("Error!")
}
else{
x<-x+.1
v(a, x)
}
}
When I set a to 1, I would expect the function to return "Yes" after recursing until x is equal to 1 as well. However, this is not the case. The function then recurses once more, setting x to 1.1 and returns the message "Error!".
I think you are running into issues with floating point precision. If you use a function designed to check equality while accounting for floating point precision, like dplyr::near(), the function gives the expected result:
v<-function(a, x)
{
#Check for current value of a and r
print(a)
print(x)
if(dplyr::near(a, x)) {
return("Yes")
}
else if(a < x) {
return("Error!")
}
else{
x<-x+.1
v(a, x)
}
}
y <- as.integer(readline(prompt ="Enter a number: "))
factorial = 1
if (y< 0){
print("Error")
} else if (y== 0)
{
print("1")
} else
{
for(i in 1:y) {
factorial = factorial * i
}
return(factorial)
}
wondering why this is giving:
Error in if (y< 0) { : missing value where TRUE/FALSE needed
is it cause the first line has data type NA_integer?
There are three possible ways to pass values to the if statement.
y <- 1
if (y > 0) print("more")
This one works as expected.
y <- 1:3
if (y > 0) print("ignores all but 1st element")
As the warning message will tell you, only the first element was used to evaluate it. You could use any or all to make this right.
y <- NA
if (y > 0) print("your error")
This case actually gives you your error. I would wager a bet that y is somehow NA. You will probably need to provide a reproducible example (with data and the whole shebang) if you'll want more assistance. Note also that it helps visually structure your code to improve readability.
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.
Please can anyone advise how I can turn the following statement into one that will do the same thing but NOT using ifelse please?
<-ifelse(y>=50, 0.2*x+0.8*y, ifelse(y<50 & x>70, y+10, ifelse(y<50 & x<70, y)))
x=80
y=60
So I the final code should give an answer of 64 - selecting the first condition. I will then test it to ensure the other 3 conditions give the correct result for varying values of x and y
Thanks a lot.
This should work:
finalmark <- (x * 0.2 + y * 0.8) * (y >= 50) + (y + 10 * (x > 70)) * (y < 50)
Something like this?
if(y>=50){
0.2*x+0.8*y
}else{
if(y<50 & x>70){
y+10
}else{
if(y<50 & x<70){
y
}else{
"OMG I did not expect this scenario"
}
}
}
try: y=45; x=70 to see why I have the last condition.
If y is a number then, once you've tested for y > = 50 then y must be less than 50 so don't keep testing for that. Similarly, once you've found x > 70 then you don't need the last ifelse. You don't have a return for x = 70. My guess is that you want to test for a <= or >= situation there.
ifelse(y>=50, 0.2*x+0.8*y, ifelse(x>70, y+10, y))
in scalar that's
if(y >= 50){
0.2*x+0.8*y
}else if(x > 70){
y+10
}else y
Given you seem to be having a hard time in general writing the logic I suggest you post a more complete question. It's possible (probable) that you're doing something here that you really don't want to do.
There are several approaches you can take. Below are a few examples of building a function 'f', so that 'f(x,y)' meets your criteria listed in the question using logic other than 'ifelse' statements.
Note: I'm also adding in one amendment to the original post, since 'x=70' would break the logic. I'm adding 'x>=70' to the second criterion.
Option 1: Use a standard 'if / else if / else' logic block. Personally, I like this option, because it's easily readable.
f <- function(x, y){
if (y>= 50){
return(0.2*x+0.8*y)
} else if (y < 50 & x >= 70){
return(y+10)
} else {
return(y)
}
}
Option 2: Combine your two logical tests (there are really only two) into a string, and use a switch. Note that the final and unnamed option is treated as an 'else'.
f <- function(x, y){
return(
switch(paste(x >= 70, y >= 50, sep=""),
TRUEFALSE = y + 10,
FALSEFALSE = y,
0.2*x+0.8*y
)
)
}
Option 3: Order your 'if' statements to reduce logical comparisons. This is the sort of thing to do if you have a large data set or very limited memory. This is slightly harder to troubleshoot, since you have to read the whole block to fully understand it. Option 1 is better if you don't have memory or cycle limitations.
f <- function(x, y){
if (y >= 50){
return(0.2*x+0.8*y)
} else {
if (x >=70){
return(y+10)
} else {
return(y)
}
}
}
There are other options, but these are the simplest that come readily to mind.