使用仅包含ISO周的数据集将ISO周汇总为几个月 [英] Aggregate ISO weeks into months with a dataset containing just ISO weeks

问题描述

我的数据位于具有如下结构的数据框中：

My data is in a dataframe which has a structure like this:

df2 <- data.frame(Year = c("2007"), Week = c(1:12), Measurement = c(rnorm(12, mean = 4, sd = 1)))

不幸的是，我没有每个测量的完整日期（例如，缺少日期），只有年份和星期（这些是ISO周）。

Unfortunately I do not have the complete date (e.g. days are missing) for each measurement, only the Year and the Weeks (these are ISO weeks).

现在，我想将一个月的测量值的中位数（例如，特定年份每月的每周测量值）汇总到一个新列月中。如果没有确切的可用日期，我找不到一种便捷的方法来执行此操作。

Now I want to aggregate the Median of a Month's worth of measurements (e.g. the weekly measurements per month of the specific year) into a new column, Months. I did not find a convenient way to do this without having the exact day of the measurements available. Any inputs are much appreciated!

推荐答案

当需要将一周分配给一个月时，尽管ISO 8601并未考虑这种情况，但可能会应用一年的第一周。（ Wikipedia ）

例如，2007年的第5周属于2月，因为第5周的星期四是2月1日。

For example, the 5th week of 2007 belongs to February, because the Thursday of the 5th week was the 1st of February.

我正在使用 data.table 和 ISOweek 软件包。请参见示例如何计算星期几。然后您可以按月进行任何汇总。

I am using data.table and ISOweek packages. See the example how to compute the month of the week. Then you can do any aggregation by month.

require(data.table)
require(ISOweek)

df2 <- data.table(Year = c("2007"), Week = c(1:12),
                  Measurement = c(rnorm(12, mean = 4, sd = 1)))

# Generate Thursday as year, week of the year, day of week according to ISO 8601
df2[, thursday_ISO := paste(Year, sprintf("W%02d", Week), 4, sep = "-")]

# Convert Thursday to date format
df2[, thursday_date := ISOweek2date(thursday_ISO)]

# Compute month
df2[, month := format(thursday_date, "%m")]
df2

Uwe建议计算年月字符串。

Suggestion by Uwe to compute a year-month string.

# Compute year-month
df2[, yr_mon := format(ISOweek2date(sprintf("%s-W%02d-4", Year, Week)), "%Y-%m")]
df2

最后，您可以对新表进行汇总或通过将中位数作为列来添加。

And finally you can do an aggregation to the new table or by adding median as a column.

df2[, median(Measurement), by = yr_mon]

df2[, median := median(Measurement), by = yr_mon]
df2

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