我是R的新手，正在旅途中学习，因此请原谅我的一些无知。我试图写我想要的东西，但是一路上遇到了一些障碍...
我从同事那里改编了这段代码，以确定力时跟踪的不同阶段。代码如下。它读取csv，然后使用带有新csv的帧引用导出。
根据特定规则定义了跟踪的每个阶段。
但是，我想知道开始推进和结束推进之间的平均总力，平均速度和平均功率？开始和结束推进的输出是单元格参考，而不是数据值。
第二，如何在代码中编写循环，以便我可以指导代码从一个文件夹读取40个csv文件，并生成具有所需输出的40个csv文件？
文件夹= Common2 \ Desktop \ R \ Jump_Files
先谢谢了。
D
我在编写均值公式以生成值时遇到麻烦。我知道会是
mean.force =平均值（start.propulsion：end.propulsion）
但这似乎不起作用？我知道这与使用值而不是单元格引用有关，但是我在这一点上被困住了
代码下方的问题...
# load required packages
require(readr)
library(tidyverse)
getwd()
# import data frame
filename <- "P01_CMJ_T01.csv"
datapath <- ''
Jump.1 = read_csv(
paste0(datapath, filename),
col_names = TRUE,
skip = 3,
trim_ws = TRUE
)
# add rownumber
Jump.1$row = 1:nrow(Jump.1)
# rename variable, sub frame to time
names(Jump.1) <- c('Frame','Time','F1','F2','sum.force','row.number')
# find sample rate
Sample.rate = 1 / diff(Jump.1$Time[1:2], lag = 1, differences = 1)
# find body mass
BM = mean(Jump.1$sum.force[1:Sample.rate])
BM.kg = BM / 9.81
sd = sd(Jump.1$sum.force[1:Sample.rate])
# add variables
Jump.1 = mutate(Jump.1, net.force = Jump.1$sum.force - BM)
Jump.1 = mutate(Jump.1, acceleration = Jump.1$net.force / BM.kg)
# velocity
Jump.1$change_vel = (Jump.1$acceleration + lag(Jump.1$acceleration, 1)) / 2 * c(NA, diff(Jump.1$Time))
Jump.1$velocity = c(0, rep(NA, nrow(Jump.1) - 1))
for (i in 2:nrow(Jump.1)) {
Jump.1$velocity[i] <- Jump.1$velocity[i - 1] + Jump.1$change_vel[i]
}
#power
Jump.1 = mutate(Jump.1, power = Jump.1$velocity * Jump.1$sum.force)
# ******************************************************************************
# Start of unweighting phase - BM - 5sd
## [only flag if remain below threshold for samplerate/10 rows]
threshold = BM - 5 * sd
# Get all the rows less than threshold
start.unweighting = which(Jump.1$sum.force < threshold)
#show(start.unweighting)
# Finds all the sub-sequences
subseq <- split(start.unweighting, cumsum(c(TRUE, diff(start.unweighting) != 1)))
#show(subseq)
# Throw away the sub-sequences less than samplerate/10 length
subseq <- subseq[sapply(subseq, length) >= Sample.rate / 10]
#show(subseq)
# The start of unweighing is then the first row of the first sub-sequence
start.unweighting <- subseq[[1]][1]
show(start.unweighting)
# ******************************************************************************
# End of unweighting phase
# All rows > theshold and AFTER start-unweigh
end.unweighting = which(Jump.1$sum.force > threshold & Jump.1$row.number > start.unweighting)
#show(end.unweighting)
# Finds all the sub-sequences
subseq <- split(end.unweighting, cumsum(c(TRUE, diff(end.unweighting) != 1)))
#show(subseq)
# Throw away the sub-sequences less than samplerate/10 length
subseq <- subseq[sapply(subseq, length) >= Sample.rate / 10]
#show(subseq)
end.unweighting <- subseq[[1]][1] - 1
show(end.unweighting)
# ******************************************************************************
# Start braking
start.braking = end.unweighting + 1
show(start.braking)
# ******************************************************************************
# End braking
# All rows with vel > 0 and AFTER start braking
end.braking = which(Jump.1$velocity > 0 &
Jump.1$row.number > start.braking)[1] - 1
show(end.braking)
# ******************************************************************************
# Start propulsion phase - vel > 0 > e
start.propulsion = end.braking + 1
show(start.propulsion)
# ******************************************************************************
# End propulsion
end.propulsion = which(Jump.1$sum.force < threshold &
Jump.1$row.number > start.propulsion)[1] - 1
show(end.propulsion)
# ******************************************************************************
# Start flight
start.flight = end.propulsion + 1
mid.flight = which(Jump.1$sum.force == 0 &
Jump.1$row.number > start.flight)[1]
# ******************************************************************************
# End flight
end.flight = which(Jump.1$sum.force > 10 -1 &
Jump.1$row.number > mid.flight)[1]
# ******************************************************************************
# Flight.time
Flight.time = (end.flight - start.flight) * 0.001
show(Flight.time)
# ******************************************************************************
# Jump.height from flight time
Jump.height = (0.125 * 9.8 * Flight.time^2)
show(Jump.height)
******************************************************************************
# Write output
output <- data.frame(
event = c(
'unweighting.start',
'unweighting.end',
'braking-start',
'braking-end',
'propulsion.start',
'propulsion.end',
'flight.start',
'flight.end',
'flight.time',
'jump.height'
),
frame = NA
)
output$frame[1] <- Jump.1$Frame[start.unweighting]
output$frame[2] <- Jump.1$Frame[end.unweighting]
output$frame[3] <- Jump.1$Frame[start.braking]
output$frame[4] <- Jump.1$Frame[end.braking]
output$frame[5] <- Jump.1$Frame[start.propulsion]
output$frame[6] <- Jump.1$Frame[end.propulsion]
output$frame[7] <- Jump.1$Frame[start.flight]
output$frame[8] <- Jump.1$Frame[end.flight]
output$frame[9] <- Flight.time
output$frame[10] <- Jump.height
show(output)
write.csv(output,
file = paste0('output-', sub('.xlsx', '.csv', filename)))