CODEWITHSUNDEEP
rtidyverse
UseR10085
UseR10085

Reputation: 8176

Calculation from a formula using tidyverse in R

I want to calculate the following indices using tidyverse package in R.

enter image description here

enter image description here

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where rm is Monthly rainfall in month m, m = 1,2,3………12

To achieve this I am using the following code

library(tidyverse) 
library(seas) 
library(openxlsx)
library(lubridate)

## get mscdata from "seas" packages
data(mscdata)
dat <- (mksub(mscdata, id=1108447))

Monthly <- dat %>% 
  mutate(Year = year(date),
         Month = month(date),
         Day = day(date)) %>% 
  group_by(Year, Month) %>% 
  summarise(Monthly = sum(precip)) 

Monthly %>% 
  group_by(Year) %>% 
  summarise(Rk = sum(Monthly),
            Ck = (1/Rk)*sum(Month*Monthly),
            Zk = sqrt((1/Rk)*sum(Month-Ck)^2*Monthly))

The calculation of Rk and Ck is matching with excel calculation. But the values of Zk is not matching. What mistake I am committing?

Upvotes: 0

Views: 274

Answers (2)

awaji98
awaji98

Reputation: 685

To match your Excel figures, you need to add a pair of parentheses:

Monthly %>% 
  group_by(Year) %>% 
  summarise(Rk = sum(Monthly),
            Ck = (1/Rk)*sum(Month*Monthly),
            Zk = sqrt((1/Rk)*sum(((Month-Ck)^2)*Monthly)))

Upvotes: 1

Ronak Shah
Ronak Shah

Reputation: 389055

Calculated the sum too early.

library(dplyr)

Monthly %>% 
  group_by(Year) %>% 
  summarise(Rk = sum(Monthly),
            Ck = (1/Rk)*sum(Month*Monthly),
            Zk = sqrt((1/Rk)*sum((Month-Ck)^2*Monthly)))

#   Year     Rk     Ck     Zk
#1  1975 1320.1 7.4674 4.1455
#2  1976 1008.3 5.5078 3.8184
#3  1977 1032.3 7.4917 3.8336
#4  1978 1016.8 6.3460 3.7901
#5  1979  986.2 7.4500 4.1851
#6  1980 1418.5 7.2960 3.9661
#7  1981 1459.2 7.0578 3.7275
#8  1982 1260.1 6.0253 4.2520
#9  1983 1489.5 6.2925 4.0069
#...
#...

Upvotes: 3

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