Suppose you are given the following code:

x

Question

Suppose you are given the following code:

x <- 1:26

mat <- matrix( x , nrow=7 )

dim( mat )

What would be the second component of dim( mat )?

BlackTom AI · Accepted Answer

The question sets up an R vector and constructs a matrix from it. 
First, x <- 1:26 creates a numeric vector of length 26 containing 1, 2, ..., 26. 
Next, mat <- matrix(x, nrow=7) asks R to shape the data into a matrix with 7 rows. When filling a matrix by default, R uses column-major order and recycles elements if needed. 
Since there are 26 elements and 7 rows, the number of columns must be such that 7 * ncol >= 26. The smallest such integer is ncol = 4, giving a 7-by-4 matrix (7 rows and 4 columns) and leaving 2 extra slots to fill, so R recycles x[1] and x[2] for those positions. 
Therefore dim(mat) returns a vector c(7, 4). The question asks for the second component of dim(mat), which is 4. 
Note that if you expected a ratio 26/7 or an exact division, that would lead to confusion, but R always reports the matrix dimensions as chosen (nrow) and the derived ncol, with recycling only affecting the contents. 
In short, the size in the second dimension corresponds to the number of columns, which in this construction is four.

BTRY3010/BTRY5010/STSCI2200/STSCI5200 Pre - Discussion #11

Suppose you are given the following code: x <- 1:26 mat <- matrix( x , nrow=7 ) dim( mat ) What would be the second component of dim( mat )?

查看解析

登录即可查看完整答案

类似问题

In a consumer society, many adults channel creativity into buying things

Economic stress and unpredictable times have resulted in a booming industry for self-help products

People born without creativity never can develop it

A product has a selling price of $20, a contribution margin ratio of 40% and fixed cost of $120,000. To make a profit of $30,000. The number of units that must be sold is: Type the number without $ and a comma. Eg: 20000

Which of the following statement regarding cost is correct:

Under the assumptions used in cost-volume-profit analysis, as the activity increases:

The CVP and break-even analysis are supported by a range of important assumptions. Which of the following is not an assumption of the CVP:

The break-even point is that at which:

更多留学生实用工具

考试浏览器助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单