问题描述
这是我关于SO的第一篇文章,所以请客气!
This is my first post on SO, so be kind!
我的问题与此模糊相关:
My question is vaguely related to this one:Double for loop in R creating a matrix
我想创建一个矩阵/数据框,我脑海中选择的方法是嵌套两个for循环,一个用于创建第一行,第二个对我需要的行重复。
I want to create a matrix/dataframe and the approach my mind has chosen is to nest two for loops, one to create the first row and the second to repeat it for the rows I nedd.
我可以成功创建第一个循环,但是对于需要的行数,我似乎无法对其进行迭代。
I could successfully create the first loop, but I can't seem to iterate it for the number of rows I need.
I '肯定有一种更好的方法可以执行此操作,无论如何,这是for循环,可为我提供第一行所需的结果:
I'm sure that there is a better way to do this, anyway, this is the for loop that gives the result I need for the first row:
x <- character(0)
for(j in 1:18){
x <- c(x, sum(it_mat[1, 2:26] == j))
}
it_mat是417行26列的矩阵,其中第一个column是具有各种名称和后续列的字符串向量ns是从1到18的随机数。
it_mat is a matrix of 417 rows and 26 columns, where the first column is a string vector with various names and the subsequent columns are randomly generated numbers from 1 to 18.
这是第一行:
[1,] "Charlie" "14" "3" "9" "14" "3" "9" "11" "11" "18" "17" "16" "5" "18" "6" "10" "3" "9" "9" "3" "18" "12" "8" "5" "5" "4"
我想创建一个矩阵/ df,在其中我计算每个名字每个数字出现多少次。
I want to create a matrix/df where I count how many times, for each name, each number appearead.
我在上面创建的for循环为第一行提供了想要的结果:
The for loop I created above gives me the result I want for the first row:
x
[1] "0" "0" "4" "1" "3" "1" "0" "1" "4" "1" "2" "1" "0" "2" "0" "1" "1" "3"
我真的不能用另一个for循环为随后的行迭代,肯定有一些我常做错的事情。
I really can't iterate it for the subsequent rows with another for loop, there must be something very mundane that I do wrong.
这是我的最佳尝试:
tr_mat <- matrix(, nrow = 147, ncol = 18)
for(i in 1:147){
x <- character()
for(j in 1:18){
x <- c(x, sum(it_mat[i, 2:26] == j))
}
tr_mat <- rbind(tr_mat, x)
}
我整个下午都在忙着,现在我放弃并与您联系,在您给我正确的方法之前,请解释一下嵌套循环中我做错了什么尝试,我可能会学到一些东西。
I went on it all afternoon and now I give up and reach out to you, before you give me the correct way to do it, please explain what I'm doing wrong in the nested for loops try, I might learn something.
我希望我能向自己解释,对不起,如果我太冗长。
谢谢您的时间。
I hope I explained myself, sorry if I've been too verbose.Thanks for your time.
推荐答案
使用底数R的另一种方法。请注意, * apply
函数是伪装的循环。
Another way, using base R. Note that *apply
functions are loops in disguise.
tr_mat2 <- sapply(1:18, function(j) sapply(1:147, function(i) sum(it_mat[i, 2:26] == j)))
请注意,此代码将生成数字矩阵,而您的 tr_mat
的模式为字符
:
Note that this code will produce a matrix of numbers, while your tr_mat
is of mode character
:
all.equal(tr_mat, tr_mat2)
#[1] "Modes: character, numeric"
DATA。
这是数据集生成代码我曾经用来测试上面的代码。
DATA.
This is the dataset generation code that I have used to test the code above.
set.seed(7966) # make the results reproducible
it_mat <- t(replicate(147, c(sample(letters, 1), sample(18, 25, TRUE))))
编辑。
按照MKR注释中的建议,以下是我对t进行修改后对OP的代码进行的更正
EDIT.
Following the suggestion in the comments by MKR, here is the OP's code corrected with my modification in the comment to his (the OP's) post.
tr_mat <- matrix(, nrow = 147, ncol = 18)
for(i in 1:147){
x <- character()
for(j in 1:18){
x <- c(x, sum(it_mat[i, 2:26] == j))
}
tr_mat[i, ] <- x
}
这是我用来生成矩阵 tr_mat
的代码,在所有中均已引用上面的.equal
测试。
This is the code that I have used to produce the matrix tr_mat
refered to in the all.equal
test above.
这篇关于用R中的两个for循环创建一个矩阵/数据框的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!