q1：r中讀入csv文件時(shí)，讀入所有的列合并為一列
A1：此時(shí)因?yàn)楸４鏁r(shí)是write.table()，，所以讀入直接read.table就行，什么參數(shù)也別加，，，如果不是直接保存的測(cè)試v、文件的話，讀入用read.csv(),參數(shù)要加header = T,sep = ','
r包下載地方：
The downloaded source packages are in
‘/tmp/Rtmp1UrAkM/downloaded_packages’
安裝位置：~/R/x86_64-pc-linux-gnu-library/4.0（服務(wù)器）
library(Matrix)
M <- Matrix(c(0, 0, 0, 2,
6, 0, -1, 5,
0, 4, 3, 0,
0, 0, 5, 0),
byrow = TRUE, nrow = 4, sparse = TRUE)
rownames(M) <- paste0("r", 1:4)
colnames(M) <- paste0("c", 1:4)
M
# 4 x 4 sparse Matrix of class "dgCMatrix"
# c1 c2 c3 c4
# r1 . . . 2
# r2 6 . -1 5
# r3 . 4 3 .
# r4 . . 5 .
認(rèn)識(shí)dgcMatrix
str(M)
# Formal class 'dgCMatrix' [package "Matrix"] with 6 slots
# ..@ i : int [1:7] 1 2 1 2 3 0 1
# ..@ p : int [1:5] 0 1 2 5 7
# ..@ Dim : int [1:2] 4 4
# ..@ Dimnames:List of 2
# .. ..$ : chr [1:4] "r1" "r2" "r3" "r4"
# .. ..$ : chr [1:4] "c1" "c2" "c3" "c4"
# ..@ x : num [1:7] 6 4 -1 3 5 2 5
# ..@ factors : list()
x：矩陣中的數(shù)字，第一列非0的數(shù)字依次寫，接著第二列第三列
M
# 4 x 4 sparse Matrix of class "dgCMatrix"
# c1 c2 c3 c4
# r1 . . . 2
# r2 6 . -1 5
# r3 . 4 3 .
# r4 . . 5 .
M@x
# [1] 6 4 -1 3 5 2 5
as.numeric(M)[as.numeric(M) != 0]
# [1] 6 4 -1 3 5 2 5
I: 存儲(chǔ)這些非0數(shù)字所在的行數(shù)，特殊的，第一行為0
M
# 4 x 4 sparse Matrix of class "dgCMatrix"
# c1 c2 c3 c4
# r1 . . . 2
# r2 6 . -1 5
# r3 . 4 3 .
# r4 . . 5 .
M@i
# [1] 1 2 1 2 3 0 1
p：If we index the columns such that the first column has index ZERO, then M@p[1] = 0, and M@p[j+2] - M@p[j+1] gives us the number of non-zero elements in column j.
In our example, when j = 2, M@p[2+2] - M@p[2+1] = 5 - 2 = 3, so there are 3 non-zero elements in column index 2 (i.e. the third column).其實(shí)就是每列非0的個(gè)數(shù)，第一個(gè)是0，最后一個(gè)是非0的個(gè)數(shù)，中間依次是前面n列的非0的個(gè)數(shù)
比如這個(gè)M中的p的形成
第一個(gè)數(shù)字是0 ，最后一個(gè)數(shù)字是矩陣中非0 的個(gè)數(shù)，也就是7，那么第二個(gè)數(shù)字就是第一列中非0的個(gè)數(shù)（1），第三個(gè)數(shù)字就是第一列的非0數(shù)加第二列的非0數(shù)，第四個(gè)數(shù)字是第三列的非0數(shù)加前面所有列的非0數(shù)，然后依次加到最后一個(gè)
M
# 4 x 4 sparse Matrix of class "dgCMatrix"
# c1 c2 c3 c4
# r1 . . . 2
# r2 6 . -1 5
# r3 . 4 3 .
# r4 . . 5 .
M@p
# [1] 0 1 2 5 7
dims:行數(shù)，列數(shù)
dimnames：行名，列名
library(Matrix)
m <- Matrix(c(0,0,0,20,5,
2,5,8,0,0,
0,0,0,0,8),
byrow = TRUE,nrow = 3,sparse = TRUE)
rownames(m) <- paste0('r',1:3)
colnames(m) <- paste0('c',1:5)
m
3 x 5 sparse Matrix of class #"dgCMatrix"
# c1 c2 c3 c4 c5
#r1 . . . 20 5
#r2 2 5 8 . .
#r3 . . . . 8
str(m)
#Formal class 'dgCMatrix'
#[package "Matrix"] with 6 slots
# ..@ i : int [1:6] 1 1 1 0 0 2
# ..@ p : int [1:6] 0 1 2 3 4 6
# ..@ Dim : int [1:2] 3 5
# ..@ Dimnames:List of 2
# .. ..$ : chr [1:3] "r1" "r2" "r3"
# .. ..$ : chr [1:5] "c1" "c2" "c3" #"c4" ...
# ..@ x : num [1:6] 2 5 8 20 5 8
# ..@ factors : list()
