hyfo (version 1.4.6)

fillGap: Fill gaps in the rainfall time series.

Description

Fill gaps in the rainfall time series.

Usage

fillGap(dataset, corPeriod = "daily")

Value

The filled dataframe

Arguments

dataset

A dataframe with first column the time, the rest columns are rainfall data of different gauges

corPeriod

A string showing the period used in the correlation computing, e.g. daily, monthly, yearly.

Details

the gap filler follows the rules below:

1. The correlation coefficient of every two columns (except time column) is calculated. the correlation coefficient calculation can be based on 'daily', 'monthly', 'annual', in each case, the daily data, the monthly mean daily data and annual mean daily data of each column will be taken in the correlation calculation.

Then the correlation matrix is got, then based on the matrix, for each column, the 1st, 2nd, 3rd,... correlated column will be got. So if there is missing value in the column, it will get data from orderly 1st, 2nd, 3rd column.

2. The simple linear regress is calculated between every two columns. When generating the linear coefficient, the incept should be force to 0. i.e. y = a*x + b should be forec to y = a*x.

3. Gap filling. E.g., on a certain date, there is a missing value in column A, then the correlation order is column B, column C, column D, which means A should take values from B firstly, if B is also missing data, then C, then D.

Assuming finally value from column C is taken. Then according to step 2, A = a*C, then the final value filled in column A is missing_in_A = a*value_in_C, a is the linear coeffcient.

References

Gap fiiling method based on correlation and linear regression.

• Hirsch, Robert M., et al. "Statistical analysis of hydrologic data." Handbook of hydrology. (1992): 17-1. Salas, Jose D. "Analysis and modeling of hydrologic time series." Handbook of hydrology 19 (1993): 1-72.

Examples

b <- read.table(text = '        Date  AAA  BBB  CCC  DDD  EEE
49 1999-12-15 24.8 21.4 25.6 35.0 17.4
50 1999-12-16   NA  0.6  1.5  6.3  2.5
51 1999-12-17   NA 16.3 20.3  NA 19.2
52 1999-12-18   13  1.6 NA  6.3  0.0
53 1999-12-19   10 36.4 12.5 26.8 24.9
54 1999-12-20   NA  0.0  0.0  0.2  0.0
55 1999-12-21  0.2  0.0  0.0  0.0  0.0
56 1999-12-22  0.0  0.0  0.0  0.0  0.0')

b1 <- fillGap(b) # if corPeriod is missing, 'daily' is taken as default.

data(testdl)
a <- extractPeriod(testdl, commonPeriod = TRUE)
a1 <- list2Dataframe(a)
a2 <- fillGap(a1)
a3 <- fillGap(a1, corPeriod = 'monthly')


# More examples can be found in the user manual on https://yuanchao-xu.github.io/hyfo/