How to find first 3 max values in a specified column? - r

Question

In R, I tried several codings but they all got errors messages. But even finally some turned out with the result, they do not look like correct. Indeed they look a bit mess up. Why?
I tried to find max values from the column of 'no. of ratings' for different smart water bottle products, but received 'volumes' column's descriptions.
> Smart_Water_Bottle_Review[which.max(Smart_Water_Bottle_Review$`no. of ratings`)]
# A tibble: 9 x 1
`volumne (oz)`
<chr>
1 16
2 17, 21
3 20
4 20.3
......
Warning message:
In which.max(Smart_Water_Bottle_Review$`no. of ratings`) :
NAs introduced by coercion
And as I changed to another column, again, another column's result other then that showed up.
Smart_Water_Bottle_Review[which.max(Smart_Water_Bottle_Review$`volumne (oz)`)]
# A tibble: 9 x 1
`keep hot (hrs)`
<chr>
1 NIL
2 0
3 NIL
......
Warning message:
In which.max(Smart_Water_Bottle_Review$`volumne (oz)`) :
NAs introduced by coercion
Simply speaking, I asked for the max value of no. of ratings, it gives the volumne; and asked for 'volumne', it gave 'keep hot'.
Plus, I asked for max, it provides everything.
Please advise how to correct these or the right syntax, thanks.

Answer 1

There are several issues here.
It looks like you have your variables stored as character, rather than numeric. The NAs introduced by coercion warning is saying that the variable was converted to numeric, but that some values weren't number-like and couldn't be converted (e.g., the NIL value). You should convert your variable to numeric first with as.numeric() and verify that all values are correctly converted.
Second, when you subset a data frame or tibble with [ using numbers and no commas, it selects the column matching that index.
Here is how I would recommend you solve this problem
library(dplyr)
Smart_Water_Bottle_Review |>
mutate(`no. of ratings` = as.numeric(`no. of ratings`)) |>
filter(`no. of ratings` == max(`no. of ratings`, na.rm = TRUE))
# alternative, notice the comma indicating to use [row, column] indexing
Smart_Water_Bottle_Review[which.max(as.numeric(Smart_Water_Bottle_Review$`no. of ratings`)) , ]
You mentioned that you wanted the top 3 values. That is most easily done by sorting the data frame:
library(dplyr)
Smart_Water_Bottle_Review |>
mutate(`no. of ratings` = as.numeric(`no. of ratings`)) |>
arrange(-`no. of ratings`) |>
slice(3)

Answer 2

for no_of_rating:
smartrating %>%
mutate(no_of_ratings_100s = as.numeric(no_of_ratings_100s)) %>%
arrange(-no_of_ratings_100s)
# A tibble: 9 x 2
Products no_of_ratings_100s
<chr> <dbl>
1 Hydrate Spark 3 Tracks (not insultaed) 37.3
2 Hydrate Spark Stainless Steel 21 oz 16.5
3 CrazyCap Self Cleaning, UV water purifyer 11.9
4 Thermos 24 oz hydration bottle w smart lid 11.5
5 LARQ 8.29
6 Philips Water GoZero UV Self-Cleaning Vacuum Insulated 3.22
7 Bellabeat 0.37
8 Equa Smart Water 0.02
for amazon_rating: (no mutate function is needed)
smartamazon %>%
arrange(-amazon_ratings_5)
# A tibble: 9 x 2
Products amazon_ratings_5
<chr> <dbl>
1 LARQ 4.5
2 CrazyCap Self Cleaning, UV water purifyer 4.4
3 Hydrate Spark Stainless Steel 21 oz 4.4
4 Hydrate Spark 3 Tracks (not insultaed) 4.4
5 Philips Water GoZero UV Self-Cleaning Vacuum Insulated 4.1
6 Equa Smart Water 4
7 Bellabeat 3.8
8 Thermos 24 oz hydration bottle w smart lid 3.7