Let's say
i = 1:2029
j = c(3,6,3,5,123,323,423,652,743,885,932)
for loop generally looks like
for (x in i) { }
in here, I would like to calculate the function for x that are not same as j
so it would be something like
for (x in i & !j) { }
but obviously, this kind of command doesn't work.
Is there are command that expresses my intention?
You can use :
for (x in i[-which(i %in% j)]) { }
Related
This is probably very simple, but I am not sure why it's not working.
For input vector b, I want to write a function which begins by checking b for any negative values. If there are any, then the function stops. Otherwise, it continues. What the function is doesn't matter.
Something like this:
F <- function(b) {
if (any(b) < 0) {
warning("error")
} else {
# the function I want to put in
}
}
Edit:
The code that works is
F <- function(b) {
if (any(b < 0)) {
stop("error")
} else {
# the function I want to put in
}
}
I am trying to check if all the elements inside a vector are the same. I am using this code:
if( isTRUE(for(i in 1:length(x)){x[1]==x[i]})){print(x[1])} else{print("several")
Now suppose
x <- c(0,0,0,0,0,0,0,0,0,0,0)
Here, the code should return "0" and if
x <- c(0,0,0,0,0,1,0,0,0,0,0)
it should return "several". In both cases I get "several", any idea why is not working as desired?
Thank u in advance.
there is a simpler way:
if (length(unique(x)) == 1) {
print(x[1])
} else {
print("several")
}
If you want to compare all components of x with the first component you should use all instead of a for loop:
if (all(x == x[1])) {
print(x[1])
} else {
print("several")
}
The result of both approaches is the same.
IS <- function(N,K,sigma,t,r,S_0,a,b,tol){
funct_1 <- function(x){
return((S_0*(exp(-0.5*(sigma^2)*t+sigma*sqrt(t)*x))*(sigma*sqrt(t)-x))+
(exp(-r*t))*K*x)
}
bisection_method <- function(a, b, tol, f = funct_1){
if (f(a)*f(b) > 0){
print("No root found.")
} else
while ((b - a)/2.0 > tol){
midpt= (a + b)/2.0
if (f(midpt) == 0){
return(midpt)
} else if (f(a)*f(midpt) < 0){
b = midpt
} else
a = midpt
}
return(midpt)
}
}
The above function will produce nothing for you. My goal that to input the values of "N,K,sigma,t,r,S_0, a,b" and somehow return "midpt" for me. I have searched a lot but could not come up with anything that makes sense. I have many problems, assume that I input everything things, then how the function "funct_1" will output expression, this expression needs to be recalled to the next function "bisection_method} along with the value of a and b then finally obtain the "midpt" value. Any suggestions are really appreciated. Please let me know if there is anything not clear to you at all.
Your main function doesn't return anything. It just creates the auxiliary functions and then do nothing. That's why you're getting no output.
Try returning the bisection method with appropriate parameters in your main function instead. I also edited so you get NULL output when no root is found.
IS <- function(N,K,sigma,t,r,S_0,a,b,tol){
funct_1 <- function(x){
return((S_0*(exp(-0.5*(sigma^2)*t+sigma*sqrt(t)*x))*(sigma*sqrt(t)-x))+
(exp(-r*t))*K*x)
}
bisection_method <- function(a, b, tol, f = funct_1){
if (f(a)*f(b) > 0){
print("No root found."); return(NULL)
} else
while ((b - a)/2.0 > tol){
midpt= (a + b)/2.0
if (f(midpt) == 0){
return(midpt)
} else if (f(a)*f(midpt) < 0){
b = midpt
} else
a = midpt
}
return(midpt)
}
return(bisection_method(a,b,tol,funct_1))
}
Figured out some parameter combination that makes sense:
IS(1,1,1,4,5,1,.1,9,10^-4)
[1] 2.000023
Basically I'm looking for an equivalent of
for (i in 1:nrow(mydata)) {
if(mydata$alive[i]) { mydata$result[i] = mydata$alive_value; }
else { mydata$result[i] = mydata$dead_value; }
}
That would be along the lines of
mydata$result <- func_if(mydata$alive,mydata$alive_value,mydata$dead_value)
Does something like that exist?
You're looking for ifelse. Documentation: http://stat.ethz.ch/R-manual/R-devel/library/base/html/ifelse.html.
mydata$result <- ifelse(mydata$alive, mydata$alive_value, mydata$dead_value)
I'm interested in creating a function Derivative that returns a function that is the derivative of some function that is passed to it, at some point. However, I want to be able to specialize this so that, for specific functions, I can return the analytical solution.
So, I'm looking for something like this:
auto Derivate(alias Function)(x)
{ return (Function(x+h) - Function(x-h))/(2h);}
auto Derivate(BSpline!(k)(x))(x)
{ return k * BSpline!(k-1)(x) + x * BSpline!(k-1)(x); }
However, I currently have BSpline defined this way:
pure Real BSpline(int k : 0, Real)(scope Real x, scope const(Real)[] t)
{
if (t[0] <= x && x < t[k+1])
return 1;
else
return 0;
}
pure Real BSpline(int k, Real)(scope Real x, scope const(Real)[] t)
{
if (t[0] <= x && x < t[k+1])
{
Real a = (x - t[0]) / (t[k] - t[0]);
Real b = (t[k+1] - x) / (t[k+1] - t[1]);
Real c = BSpline!(k-1,Real)(x, t[0..k+1]);
Real d = BSpline!(k-1,Real)(x, t[1..k+2]);
Real rv = (c?c*a:c) + (d?d*b:d);
return rv;
}
else
return 0;
}
So the type signature on BSpline is going to be Real function(Real,Real), which isn't differentiable from any other kind of function. Is the way to solve this to create a "BSpline" class with opCall defined? Or can I do some sort of typedef to identify this function?
Thanks!
To specialize a template, you have to use the : notation:
auto foo(alias F_, X_)(X_ x) {
/* code here ... */
}
auto foo(alias F_ : BSpline, X_)(X_ x) {
/* specialized version here */
}