I have a problem creating ride_length in capstone project

I am new in the R studio and i encounter some sort of problem in the case study I am working with, when I enter a code chunk - all_trips$ride_length <- difftime(all_trips$ended_at,all_trips$started_at) -
and the R studio showing this - Error in as.POSIXlt.character(x, tz, ...) :
character string is not in a standard unambiguous format -

You have not shared your data, so I can't be sure what the exact problem is. I suspect that your started_at and ended_at columns are characters with a month/day/year hour:minute format and R will not convert that to numeric dates without being told what the format is. There are MANY date formats and guessing is not a good idea.
Here is an example with invented data. It shows the error you got and a way to convert the columns into numeric dates so you can do calculations with them. The steps where I print the data frame and show its structure with the str() function are just for illustration and are not necessary.
If your dates are not in the format I guessed, you will have to adjust the format argument in the as.POSIXlt() function.

DF <- data.frame(started_at = c("1/21/2024 11:17", "1/30/2024 14:09"),
                 ended_at = c("1/21/2024 12:05", "1/30/2024 14:21"))
DF
#>        started_at        ended_at
#> 1 1/21/2024 11:17 1/21/2024 12:05
#> 2 1/30/2024 14:09 1/30/2024 14:21
str(DF)  #the columns are characters
#> 'data.frame':    2 obs. of  2 variables:
#>  $ started_at: chr  "1/21/2024 11:17" "1/30/2024 14:09"
#>  $ ended_at  : chr  "1/21/2024 12:05" "1/30/2024 14:21"
DF$started_at <- as.POSIXlt(DF$started_at) #conversion fails. The function trys formats with the patter year/month/day & month = 21 or 30 is an error
#> Error in as.POSIXlt.character(DF$started_at): character string is not in a standard unambiguous format
DF$started_at <- as.POSIXlt(DF$started_at, format = "%m/%d/%Y %H:%M") #tell the function what the date format is
DF$ended_at <- as.POSIXlt(DF$ended_at, format = "%m/%d/%Y %H:%M") #tell the function what the date format is
DF
#>            started_at            ended_at
#> 1 2024-01-21 11:17:00 2024-01-21 12:05:00
#> 2 2024-01-30 14:09:00 2024-01-30 14:21:00
str(DF)
#> 'data.frame':    2 obs. of  2 variables:
#>  $ started_at: POSIXlt, format: "2024-01-21 11:17:00" "2024-01-30 14:09:00"
#>  $ ended_at  : POSIXlt, format: "2024-01-21 12:05:00" "2024-01-30 14:21:00"
#now you can calculate with the date columns

Created on 2024-02-23 with reprex v2.0.2

thank you so much for answering my question, but in contrast to your saying this is the whole code chunk I am writing

Please post the output of

dput(all_trips[1:10, c("started_at", "ended_at")])

Do not post a picture of the output. Copy the output from the console and paste it into your reply.

all_trips <- all_trips %>%

  • select(-c(start_lat, start_lng, end_lat, end_lng, birthyear, gender, "tripduration"))

colnames(all_trips)
[1] "ride_id" "started_at" "ended_at" "rideable_type"
[5] "start_station_id" "start_station_name" "end_station_id" "end_station_name"
[9] "member_casual"
nrow(all_trips)
[1] 791956
dim(all_trips)
[1] 791956 9
head(all_trips)

A tibble: 6 × 9

ride_id started_at ended_at rideable_type start_station_id start_station_name end_station_id

1 21742443 1/1/2019 0:… 1/1/201… 2167 199 Wabash Ave & Gran… 84
2 21742444 1/1/2019 0:… 1/1/201… 4386 44 State St & Randol… 624
3 21742445 1/1/2019 0:… 1/1/201… 1524 15 Racine Ave & 18th… 644
4 21742446 1/1/2019 0:… 1/1/201… 252 123 California Ave & … 176
5 21742447 1/1/2019 0:… 1/1/201… 1170 173 Mies van der Rohe… 35
6 21742448 1/1/2019 0:… 1/1/201… 2437 98 LaSalle St & Wash… 49

:information_source: 2 more variables: end_station_name , member_casual

str(all_trips)
tibble [791,956 × 9] (S3: tbl_df/tbl/data.frame)
ride_id : chr [1:791956] "21742443" "21742444" "21742445" "21742446" ... started_at : chr [1:791956] "1/1/2019 0:04" "1/1/2019 0:08" "1/1/2019 0:13" "1/1/2019 0:13" ...
ended_at : chr [1:791956] "1/1/2019 0:11" "1/1/2019 0:15" "1/1/2019 0:27" "1/1/2019 0:43" ... rideable_type : chr [1:791956] "2167" "4386" "1524" "252" ...
start_station_id : num [1:791956] 199 44 15 123 173 98 98 211 150 268 ... start_station_name: chr [1:791956] "Wabash Ave & Grand Ave" "State St & Randolph St" "Racine Ave & 18th St" "California Ave & Milwaukee Ave" ...
end_station_id : num [1:791956] 84 624 644 176 35 49 49 142 148 141 ... end_station_name : chr [1:791956] "Milwaukee Ave & Grand Ave" "Dearborn St & Van Buren St ()" "Western Ave & Fillmore St ()" "Clark St & Elm St" ...
$ member_casual : chr [1:791956] "Subscriber" "Subscriber" "Subscriber" "Subscriber" ...
summary(all_trips)
ride_id started_at ended_at rideable_type start_station_id
Length:791956 Length:791956 Length:791956 Length:791956 Min. : 2.0
Class :character Class :character Class :character Class :character 1st Qu.: 77.0
Mode :character Mode :character Mode :character Mode :character Median :174.0
Mean :204.4
3rd Qu.:291.0
Max. :675.0

start_station_name end_station_id end_station_name member_casual
Length:791956 Min. : 2.0 Length:791956 Length:791956
Class :character 1st Qu.: 77.0 Class :character Class :character
Mode :character Median :174.0 Mode :character Mode :character
Mean :204.4
3rd Qu.:291.0
Max. :675.0
NA's :1

table(all_trips$member_casual)

casual   Customer     member Subscriber 
 48480      23163     378407     341906 

all_trips <- all_trips %>%

  • mutate(member_casual = recode(member_casual
  •                             ,"Subscriber" = "member"
    
  •                             ,"Customer" = "casual"))
    

all_trips <- all_trips %>%

  • mutate(member_casual = recode(member_casual
  •                             ,"Subscriber" = "member"
    
  •                             table(all_trips$member_casual),"Customer" = "casual"))
    

Error: unexpected symbol in:
" ,"Subscriber" = "member"
table"

table(all_trips$member_casual)

casual member
71643 720313

all_trips$date <- as.Date(all_trips$started_at)
all_trips$month <- format(as.Date(all_trips$date), "%m")
all_trips$day <- format(as.Date(all_trips$date), "%d")
all_trips$year <- format(as.Date(all_trips$date), "%Y")
all_trips$day_of_week <- format(as.Date(all_trips$date), "%A")
all_trips$ride_length <- difftime(all_trips$ended_at,all_trips$started_at)

This is the output in my R, I hope it helps you what is the problem thank you.

Please post the output I asked for.

dput(all_trips[1:10, c("started_at", "ended_at")])
structure(list(started_at = c("1/1/2019 0:04", "1/1/2019 0:08",
"1/1/2019 0:13", "1/1/2019 0:13", "1/1/2019 0:14", "1/1/2019 0:15",
"1/1/2019 0:16", "1/1/2019 0:18", "1/1/2019 0:18", "1/1/2019 0:19"
), ended_at = c("1/1/2019 0:11", "1/1/2019 0:15", "1/1/2019 0:27",
"1/1/2019 0:43", "1/1/2019 0:20", "1/1/2019 0:19", "1/1/2019 0:19",
"1/1/2019 0:20", "1/1/2019 0:47", "1/1/2019 0:24")), row.names = c(NA,
-10L), class = c("tbl_df", "tbl", "data.frame"))

This sir Im sorry I am new to this

Here is the sort of code I was suggesting. First convert started_at and ended_at into numeric dates, then do any transformation you need.

all_trips <- structure(list(started_at = c("1/1/2019 0:04", "1/1/2019 0:08",
                                           "1/1/2019 0:13", "1/1/2019 0:13", "1/1/2019 0:14", "1/1/2019 0:15",
                                           "1/1/2019 0:16", "1/1/2019 0:18", "1/1/2019 0:18", "1/1/2019 0:19"), 
                            ended_at = c("1/1/2019 0:11", "1/1/2019 0:15", "1/1/2019 0:27",
                                         "1/1/2019 0:43", "1/1/2019 0:20", "1/1/2019 0:19", "1/1/2019 0:19",
                                         "1/1/2019 0:20", "1/1/2019 0:47", "1/1/2019 0:24")), 
                       row.names = c(NA, -10L), class = c("tbl_df", "tbl", "data.frame"))

all_trips$started_at <- as.POSIXct(all_trips$started_at, format = "%m/%d/%Y %H:%M") 
all_trips$ended_at <- as.POSIXct(all_trips$ended_at, format = "%m/%d/%Y %H:%M") 

all_trips$date <- as.Date(all_trips$started_at)
all_trips$month <- format(all_trips$date, "%m")
all_trips$day <- format(all_trips$date, "%d")
all_trips$year <- format(all_trips$date, "%Y")
all_trips$day_of_week <- format(all_trips$date, "%A")
all_trips$ride_length <- difftime(all_trips$ended_at,all_trips$started_at)
all_trips
#>             started_at            ended_at       date month day year
#> 1  2019-01-01 00:04:00 2019-01-01 00:11:00 2019-01-01    01  01 2019
#> 2  2019-01-01 00:08:00 2019-01-01 00:15:00 2019-01-01    01  01 2019
#> 3  2019-01-01 00:13:00 2019-01-01 00:27:00 2019-01-01    01  01 2019
#> 4  2019-01-01 00:13:00 2019-01-01 00:43:00 2019-01-01    01  01 2019
#> 5  2019-01-01 00:14:00 2019-01-01 00:20:00 2019-01-01    01  01 2019
#> 6  2019-01-01 00:15:00 2019-01-01 00:19:00 2019-01-01    01  01 2019
#> 7  2019-01-01 00:16:00 2019-01-01 00:19:00 2019-01-01    01  01 2019
#> 8  2019-01-01 00:18:00 2019-01-01 00:20:00 2019-01-01    01  01 2019
#> 9  2019-01-01 00:18:00 2019-01-01 00:47:00 2019-01-01    01  01 2019
#> 10 2019-01-01 00:19:00 2019-01-01 00:24:00 2019-01-01    01  01 2019
#>    day_of_week ride_length
#> 1      Tuesday      7 mins
#> 2      Tuesday      7 mins
#> 3      Tuesday     14 mins
#> 4      Tuesday     30 mins
#> 5      Tuesday      6 mins
#> 6      Tuesday      4 mins
#> 7      Tuesday      3 mins
#> 8      Tuesday      2 mins
#> 9      Tuesday     29 mins
#> 10     Tuesday      5 mins

Created on 2024-02-24 with reprex v2.0.2

It works, it really works man, Thank very much for your help Sir

A hello Sir, sorry for the my dumbness in this, The code we write is good but there is another problem that I encounter here, the start_station_name is gone when I copy the code you send to me, What should I do , will I create another data frame for this ?

Without seeing your code, I can't say what the problem is. You need to post the code from where you last knew that the start_station_name column was present to the point where it is not present and you need to post some data. For the code, remove lines that do not change the data frame, such as uses of str() or is.numeric() where you are just confirming some aspect of your process. When you paste the code here, places lines with three back ticks before and after the pasted code, like this
```
Pasted code goes here
```
For the data, I assume you need to post some of the all_trips data frame. Post the output of

dput(head(all_trips))

As with the code, put line with three back ticks before and after the output of dput().
Please test whether the simplified code still shows the problem.

Im sorry for the delay,

all_trips <- bind_rows(q1_2019, q1_2020)#, q3_2019)#, q4_2019, q1_2020)

This is the code I wrote when the last time I saw start_station_name , and when the time Im encoding the code chunks you provided all the vanish.


this is aftermath of the code I wrote, please dont be angry with me

Please post the code that was run between the time when all_trips had the column start_station_name and when the column was gone. Also post the output of dput(head(all_trips)). Posting images of the data does not help me understand what removed the column from your data. Please see my previous post for an explanation of how to post code and output.

this code has the column name start_station_name

all_trips <- bind_rows(q1_2019, q1_2020)#, q3_2019)#, q4_2019, q1_2020)

dput(head(all_trips))
structure(list(ride_id = c("21742443", "21742444", "21742445",
"21742446", "21742447", "21742448"), started_at = c("1/1/2019 0:04",
"1/1/2019 0:08", "1/1/2019 0:13", "1/1/2019 0:13", "1/1/2019 0:14",
"1/1/2019 0:15"), ended_at = c("1/1/2019 0:11", "1/1/2019 0:15",
"1/1/2019 0:27", "1/1/2019 0:43", "1/1/2019 0:20", "1/1/2019 0:19"
), rideable_type = c("2167", "4386", "1524", "252", "1170", "2437"
), start_station_id = c(199, 44, 15, 123, 173, 98), start_station_name = c("Wabash Ave & Grand Ave",
"State St & Randolph St", "Racine Ave & 18th St", "California Ave & Milwaukee Ave",
"Mies van der Rohe Way & Chicago Ave", "LaSalle St & Washington St"
), end_station_id = c(84, 624, 644, 176, 35, 49), end_station_name = c("Milwaukee Ave & Grand Ave",
"Dearborn St & Van Buren St ()", "Western Ave & Fillmore St ()",
"Clark St & Elm St", "Streeter Dr & Grand Ave", "Dearborn St & Monroe St"
), member_casual = c("member", "member", "member", "member",
"member", "member"), date = structure(c(-719143, -719143, -719143,
-719143, -719143, -719143), class = "Date"), month = c("01",
"01", "01", "01", "01", "01"), day = c("20", "20", "20", "20",
"20", "20"), year = c("1", "1", "1", "1", "1", "1"), day_of_week = c("Saturday",
"Saturday", "Saturday", "Saturday", "Saturday", "Saturday")), row.names = c(NA,
-6L), class = c("tbl_df", "tbl", "data.frame"))

and this code when the start_station_name is gone

all_trips <- structure(list(started_at = c("1/1/2019 0:04", "1/1/2019 0:08",
                                           "1/1/2019 0:13", "1/1/2019 0:13", "1/1/2019 0:14", "1/1/2019 0:15",
                                           "1/1/2019 0:16", "1/1/2019 0:18", "1/1/2019 0:18", "1/1/2019 0:19"), 
                            ended_at = c("1/1/2019 0:11", "1/1/2019 0:15", "1/1/2019 0:27",
                                         "1/1/2019 0:43", "1/1/2019 0:20", "1/1/2019 0:19", "1/1/2019 0:19",
                                         "1/1/2019 0:20", "1/1/2019 0:47", "1/1/2019 0:24")), 
                       row.names = c(NA, -10L), class = c("tbl_df", "tbl", "data.frame"))

You should not be using this code

all_trips <- structure(list(started_at = c("1/1/2019 0:04", "1/1/2019 0:08",
                                           "1/1/2019 0:13", "1/1/2019 0:13", "1/1/2019 0:14", "1/1/2019 0:15",
                                           "1/1/2019 0:16", "1/1/2019 0:18", "1/1/2019 0:18", "1/1/2019 0:19"), 
                            ended_at = c("1/1/2019 0:11", "1/1/2019 0:15", "1/1/2019 0:27",
                                         "1/1/2019 0:43", "1/1/2019 0:20", "1/1/2019 0:19", "1/1/2019 0:19",
                                         "1/1/2019 0:20", "1/1/2019 0:47", "1/1/2019 0:24")), 
                       row.names = c(NA, -10L), class = c("tbl_df", "tbl", "data.frame"))

I used that to recreate a small part of your data set so I could show how to calculate the ride-length column.

The dput() output you just posted makes a data frame with some columns that look wrong. Here is what you posted.


all_trips <- structure(list(ride_id = c("21742443", "21742444", "21742445",
                           "21742446", "21742447", "21742448"), 
               started_at = c("1/1/2019 0:04", "1/1/2019 0:08", "1/1/2019 0:13", 
                              "1/1/2019 0:13", "1/1/2019 0:14","1/1/2019 0:15"), 
               ended_at = c("1/1/2019 0:11", "1/1/2019 0:15","1/1/2019 0:27", "1/1/2019 0:43", 
                            "1/1/2019 0:20", "1/1/2019 0:19"), 
               rideable_type = c("2167", "4386", "1524", "252", "1170", "2437"), 
               start_station_id = c(199, 44, 15, 123, 173, 98), 
               start_station_name = c("Wabash Ave & Grand Ave","State St & Randolph St", 
                                      "Racine Ave & 18th St", "California Ave & Milwaukee Ave",
                                      "Mies van der Rohe Way & Chicago Ave", "LaSalle St & Washington St"), 
               end_station_id = c(84, 624, 644, 176, 35, 49), 
               end_station_name = c("Milwaukee Ave & Grand Ave","Dearborn St & Van Buren St ()", 
                                    "Western Ave & Fillmore St ()","Clark St & Elm St", "Streeter Dr & Grand Ave", 
                                    "Dearborn St & Monroe St"), 
               member_casual = c("member", "member", "member", "member","member", "member"), 
               date = structure(c(-719143, -719143, -719143,-719143, -719143, -719143), class = "Date"), 
               month = c("01","01", "01", "01", "01", "01"), 
               day = c("20", "20", "20", "20","20", "20"), 
               year = c("1", "1", "1", "1", "1", "1"), 
               day_of_week = c("Saturday","Saturday", "Saturday", "Saturday", "Saturday", "Saturday")), 
          row.names = c(NA,-6L), 
          class = c("tbl_df", "tbl", "data.frame"))

All of the started_at and ended_at dates are 1/1/2019, yet the day column has values of "20" and year values of "1".
I think what you need to do is read in the all_trips data from its source and then run this code.

all_trips$started_at <- as.POSIXct(all_trips$started_at, format = "%m/%d/%Y %H:%M") 
all_trips$ended_at <- as.POSIXct(all_trips$ended_at, format = "%m/%d/%Y %H:%M") 

all_trips$date <- as.Date(all_trips$started_at)
all_trips$month <- format(all_trips$date, "%m")
all_trips$day <- format(all_trips$date, "%d")
all_trips$year <- format(all_trips$date, "%Y")
all_trips$day_of_week <- format(all_trips$date, "%A")
all_trips$ride_length <- difftime(all_trips$ended_at,all_trips$started_at)

That should get you a version of all_trips that has the columns you want.

it works smoothly Sir, thank you for helping I will just post anything here If I encounter a problem, once again thank you Sir and have a good day.

Hi sir again, thank you again for the help but can you help a little bit in my ggplot so here is the code

all_trips_v2 %>% 
  mutate(weekday = wday(started_at, label = TRUE)) %>%  
  group_by(member_casual, weekday) %>%  
  summarise(number_of_rides = n()							 
            ,average_duration = mean(ride_length)) %>% 		
  arrange(member_casual, weekday)	

this the start of my ggplot and then another code to create the plot

all_trips_v2 %>% 
  mutate(weekday = wday(started_at, label = TRUE)) %>% 
  group_by(member_casual, weekday) %>% 
  summarise(number_of_rides = n()
            ,average_duration = mean(ride_length)) %>% 
  arrange(member_casual, weekday)  %>% 
  ggplot(aes(x = weekday, y = number_of_rides, fill = member_casual)) +
  geom_col(position = "dodge")

my ggplot is is blank.

I don't see anything wrong with your code. I suspect the data are not what you think they are. Please post the output of

summary(all_trips_v2)

summary(all_trips_v2)
ride_id started_at ended_at
Length:6 Min. :2019-01-01 00:04:00 Min. :2019-01-01 00:11:00
Class :character 1st Qu.:2019-01-01 00:09:15 1st Qu.:2019-01-01 00:16:00
Mode :character Median :2019-01-01 00:13:00 Median :2019-01-01 00:19:30
Mean :2019-01-01 00:11:10 Mean :2019-01-01 00:22:30
3rd Qu.:2019-01-01 00:13:45 3rd Qu.:2019-01-01 00:25:15
Max. :2019-01-01 00:15:00 Max. :2019-01-01 00:43:00

rideable_type start_station_id start_station_name end_station_id end_station_name
Length:6 Min. : 15.0 Length:6 Min. : 35.00 Length:6
Class :character 1st Qu.: 57.5 Class :character 1st Qu.: 57.75 Class :character
Mode :character Median :110.5 Mode :character Median :130.00 Mode :character
Mean :108.7 Mean :268.67
3rd Qu.:160.5 3rd Qu.:512.00
Max. :199.0 Max. :644.00

member_casual date month day
Length:6 Min. :2019-01-01 Length:6 Length:6
Class :character 1st Qu.:2019-01-01 Class :character Class :character
Mode :character Median :2019-01-01 Mode :character Mode :character
Mean :2019-01-01
3rd Qu.:2019-01-01
Max. :2019-01-01

 year              day_of_week  ride_length   

Length:6 Sunday :0 Min. : 4.00
Class :character Monday :0 1st Qu.: 6.25
Mode :character Tuesday :6 Median : 7.00
Wednesday:0 Mean :11.33
Thursday :0 3rd Qu.:12.25
Friday :0 Max. :30.00
Saturday :0