[英]How to count the number of pixels in a file in R?
whenever the values in cus
range between 0-1, calculate the corresponding average in cor
and return the result, do the same thing with 2-3,3-4,5-6,7-8.no data values are assigned as NA. 每当
cus
值介于0-1之间时,计算cor
的相应平均值并返回结果,请对2-3、3-4、5-6、7-8进行相同的操作。没有将数据值分配为NA 。
1- to read corr
: 1-读取
corr
:
conne <- file("C:\\corr.bin","rb")
corr <- readBin(conne, numeric(), size=4, n=1440*720, signed=TRUE)
#please assume a matrix of 720*1440 dimnsions
2- to read cus
: 2-阅读
cus
:
conne1 <- file("C:\\use.bin","rb")
cus <- readBin(conne1, numeric(), size=4, n=1440*720, signed=TRUE)
#please assume a matrix of 720*1440 dimnsions
How about using data.table
. 如何使用
data.table
。 I am assuming that the values in cus
are actually 1:7 (so basically not sure why you need cusBreak
). 我假设中的值
cus
实际上是1:7(所以基本上不知道为什么你需要cusBreak
)。 We create a variable to count the number of pixels used to find the mean
of each group (and don't forget to include na.rm
if you have NAs in your data): 我们创建一个变量来计算用于查找每个组
mean
的像素数(如果您的数据中包含NA,请不要忘记添加na.rm
):
require( data.table )
DT <- data.table( "Cus" = as.vector(cus) , "Corr" = as.vector(corr) )
DT[ , Pix:=( ifelse( is.na( DT$Corr ) , 0 , 1 ) ) ]
DT[ , list( "Mean" = mean(Corr,na.rm=TRUE) , "Sum" = sum(Pix) ) , by = Cus ]
# Data
set.seed(12345)
corr <- matrix( rnorm(16) , 4 )
cus <- matrix( sample(0:7,16,repl=T) , 4 )
cus
# [,1] [,2] [,3] [,4]
#[1,] 1 6 6 2
#[2,] 5 7 3 2
#[3,] 2 4 7 0
#[4,] 2 1 6 0
# Create data.table
DT <- data.table( "Cus" = as.vector(cus) , "Corr" = as.vector(corr) )
# Order by Cus
setkey(DT,Cus)
# Variable to count pixels
DT[ , Pix:=( ifelse( is.na( DT$Corr ) , 0 , 1 ) ) ]
# Get meean of corr grouped by cus
DT[ , list( "Mean" = mean(Corr , na.rm = TRUE ) , "Sum" = sum(Pix) ) , by = Cus ]
# Cus Mean Pixels
#1: 1 0.15467236 2
#2: 5 0.70946602 1
#3: 2 0.08201096 4
#4: 6 0.71301325 3
#5: 7 -0.96710189 2
#6: 4 0.63009855 1
#7: 3 -0.91932200 1
#8: 0 0.03318392 2
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