使用函数而不是for循环来标识向量中的顺序更改

您可以使用which和diff帮助确定发生下降趋势的位置,并使用它cumsum来填写组成员资格.

# set up new column with all 0s
df$downward.trend.seq <- 0
# use diff to identify indices to change to 1
df$downward.trend.seq[which(c(NA, diff(df$measurement)) > 0)] <- 1
# use cumsum to fill in proper group membership
df$downward.trend.seq <- cumsum(df$downward.trend.seq)