R中的错误:当我尝试应用外部函数时: [英] An Error in R: When I try to apply outer function:
问题描述
这是我的代码:
步骤1:定义一个反函数,稍后我将使用
Here is my code: Step1: Define a inverse function which I will use later
inverse = function (f, lower = -100, upper = 100) {
function (y) uniroot((function (x) f(x) - y), lower = lower, upper = upper)[1]
}
Step2:这是我的函数及其反函数:
Step2: Here is my functions and their inverse:
F1<-function(x,m1,l,s1,s2){l*pnorm((x-m1)/s1)+(1-l)*pnorm((x+m1)/s2)}
F1_inverse = inverse(function(x) F1(x,1,0.1,2,1) , -100, 100)
F2<-function(x,m2,l,s1,s2){l*pnorm((x-m2)/s1)+(1-l)*pnorm((x+m2)/s2)}
F2_inverse = inverse(function(x) F1(x,1,0.1,2,1) , -100, 100)
第3步:这是结合以上功能的最终函数(我确定该函数正确):
Step3: Here is my final function which combines the above functions (I am sure the function is correct):
copwnorm<-function(x,y,l,mu1,mu2,sd1,sd2) {
(l*dnorm(((F1_inverse(pnorm(x))$root-mu1)/sd1))*
dnorm(((F2_inverse(pnorm(y))$root-mu2)/sd1)))
}
Step4:我想在Step 中为该函数创建轮廓图,在此处输入代码
3:
Step4: I want to create a contour plot for the function in Stepenter code here
3:
x<-seq(-2,2,0.1)
y<-seq(-2,2,0.1)
z<-outer(x,y,copwnorm)
contour(x,y,z,xlab="x",ylab="y",nlevels=15)
这里是问题出在我试图应用函数external(x,y,copwnorm),它给我一个错误:'zeroin'中的函数值无效。我可以问一下如何解决这个问题吗?
Here is the problem comes in, when I tried to apply function outer(x,y,copwnorm), it gives me an error:invalid function value in 'zeroin'. May I ask how to solve this problem?
推荐答案
我认为假设 outer(x,y,FUN)
为每个必需的对 x [i]调用一次函数参数(
和 FUN
) ] y [j]
。实际上,在创建所有可能的对并组合每个元素之后,外部
仅调用 FUN
一次 x
和每个 y
元素的方式,类似于函数 expand.grid
。
I believe it is a very commom misconception to assume that outer(x, y, FUN)
calls the function parameter (FUN
) once for each required pair x[i]
and y[j]
. Actually, outer
calls FUN
only once, after creating all possible pairs, combining every element of x
with every element of y
, in a manner similar to the function expand.grid
.
我将通过一个示例来说明这一点:考虑一下此函数,它是产品的包装,每次打印时都会显示一条消息
I'll show that with an example: consider this function, which is a wrapper for the product and print a message every time it's called:
f <- function(x,y)
{
cat("f called with arguments: x =", capture.output(dput(x)), "y =", capture.output(dput(y)), "\n")
x*y
}
此函数是自然矢量化的,因此我们可以使用矢量参数来调用它: / p>
This function is "naturally" vectorized, so we can call it with vector arguments:
> f(c(1,2), c(3,4))
f called with arguments: x = c(1, 2) y = c(3, 4)
[1] 3 8
使用外部
:
> outer(c(1,2), c(3,4), f)
f called with arguments: x = c(1, 2, 1, 2) y = c(3, 3, 4, 4)
[,1] [,2]
[1,] 3 4
[2,] 6 8
注意生成的组合。
如果我们不能保证函数可以处理向量参数,那么有一个简单的技巧以确保该功能对于组合中的每对仅调用一次: Vectorize
。这将创建另一个函数,该函数将对参数中的每个元素调用一次原始函数:
If we can't guarantee that the function can handle vector arguments, there is a simple trick to ensure the function gets called only once for each pair in the combinations: Vectorize
. This creates another function that calls the original function once for each element in the arguments:
> Vectorize(f)(c(1,2),c(3,4))
f called with arguments: x = 1 y = 3
f called with arguments: x = 2 y = 4
[1] 3 8
所以我们可以制作一个安全的 外部
:
So we can make a "safe" outer
with it:
> outer(c(1,2), c(3,4), Vectorize(f))
f called with arguments: x = 1 y = 3
f called with arguments: x = 2 y = 3
f called with arguments: x = 1 y = 4
f called with arguments: x = 2 y = 4
[,1] [,2]
[1,] 3 4
[2,] 6 8
在这种情况下,结果相同,因为 f
是用矢量化方式编写的,即,因为 *
是矢量化的。但是,如果您在编写函数时没有考虑到这一点,则直接在外部
中使用它可能会失败,或者(更糟糕的)结果也会出错。
In this case, the results are the same because f
was written in a vectorized way, i.e., because "*"
is vectorized. But if your function is not written with this in mind, using it directly in outer
may fail or (worse) may give wrong results.
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