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Kan Nishida
co-founder/CEO
Exploratory
Summary
Beginning of 2016, launched Exploratory, Inc. to make
Data Science available for everyone.
Prior to Exploratory, Kan was a director of development at
Oracle leading development teams for building various
Data Science products in areas including Machine
Learning, BI, Data Visualization, Mobile Analytics, Big Data,
etc.
While at Oracle, Kan also provided training and consulting
services to help organizations transform with data.
@KanAugust
Instructor

Mission
Make Data Science available for everyone

Data Science is not just for Engineers and Statisticians.
Exploratory makes it possible for Everyone to do Data Science.
The Third Wave

First Wave Second Wave Third Wave
Proprietary Open Source
UI & Programming Programming
201620001976
Monetization Commoditization Democratization
Statisticians Data Scientists
Smart Waves - Machine Learning / AI
Algorithms
Experience
Tools
Open Source
UI & Automation
Business Users
Theme
Users
Exploratory

Questions
Data Science Workﬂow
CommunicationData Access
Data Wrangling
Data
Visualization
Machine
Learning /
Statistics
Exploration

Questions
What you can do with Exploratory
CommunicationData Access
Data Wrangling
Visualization
Machine Learning /
Statistics
Exploratory
Data
Analysis

Questions CommunicationData Access
Data Wrangling
Visualization
Exploratory
Data
Analysis
Machine Learning /
Statistics

• User Activity Data
• Each row represents an user access for a ﬁctional online service.
• There are 6 columns, timestamp, user id, event type, IP address,
OS, and OS version.
• Download EDF
Data

Data Wrangling: Working with Date / Time Data and Visualizing It

Questions
1. What is the duration (date range) of this data?
2. What is DAU (Daily Active Users) and how it’s
been changed over time?
3. Which days of week (e.g. Monday) and hours
are more active?

Character vs. Date/Time
Data Type

Date data is recognized as character.
Dates duration is
igonored
Sorted as
character.
e.g. 10 (Oct.)
comes after 1
(Jan)
Data: Date-unicorn.csv

Various transformation on date data is available
Data is sorted as dates.
Duration
honors
date
interval.

Date vs. POSIXct
Data Type for Data & Time

Date POSIXct
Only Date
Both
Date and Time

By making it to Date & Time data type, you
can do a lot of cool things.

1. Convert Character to Date / Time
2. Extract Date / Time Attributes
3. Filter with Date / Time
4. Duration
5. Round Date / Time
6. Timezone
Common Tasks

Only codes you need to know
• Year
• Month
• Day
• Hour
• Minute
• Second

Date Format
2017-01-01
y m d
2017-01-01 08:10:10
y m d h m s

ymd("2015-10-01")
ymd("2015/10/01")
ymd("Created on 2015 October 1st")
ymd

ymd_hms("2015-01-10T06:10:15")
ymd_hms("2015/01/10 06:10:15 UTC")
ymd_hms("Created on 15-01-10 at 06:10:15 AM")
ymd_hms

mdy("01-10-2015")
mdy("01/10/2015")
mdy("Created on 1 10 2015")
mdy

mdy_hms("10-01-2015T06:10:15")
mdy_hms("10/01/2015T06:10:15")
mdy_hms("Created on 10 1 2015")
mdy_hms

• 2017-06-24
• June
• 24th
• 2017
• 175th day in 2017
• Saturday
Date Attributes
• 2017-06-24

• 2017-01-01 08:10:10
Time Attributes

• AM
• 8 hours
• 10 minutes
• 10 seconds
Time Attributes
• 2017-01-01 08:10:10

month(start_time, label = TRUE)
→ Jan, Feb, Mar …
Extract Month

Extract Month
From Column Header Menu
1. Select “Extract”
2. Select “Month - Short Name (Jan)”

wday(start_time, label = TRUE)
→ Sun, Mon, Tue …
Extract Day of Week

Extract Day of Week
1. Select “Extract”
2. Select “Day of Week - Short Name (Mon)”

Ordinal - Ordered Factor
• Month, Day of Week should
be sorted in the natural
order.
• R’s factor data type
supports ‘Order’ information.
• Functions like ‘wday’,
‘month’, take care of it.

Relative Date
• Previous Year
• This Year
• Last <N> Years
• Year to Date
Year

Today20182017
Previous Year
This Year
2016
Last 2 Years
2019
Year to Date
Relative Date

Absolute Date
• equal to / not equal to
• is in / is not in
• earlier than
• later than
• between

Today20182017
Year == 2017
Date > 1 year ago
2016
Year > 2016
2019
Between 2017-06-01 and 2018-1-30
Absolute Date

3 weeks
4 weeks
2 weeks
First Date Last Date
Duration

last_activity_date - ﬁrst_activity_date

1. Calculate lifetime for each user

Duration is calculated and stored in ‘seconds’ (unit) as ‘diﬀtime’ data type.

1. Select “Change Data Type”
2. Select “Convert to Number”
3. Select “Days”
2. Convert the lifetime to numeric data type (in days)

2. Convert the lifetime to numeric data type (in days)

as.numeric(duration, units = “days”)
You can set ‘units’ inside ‘as.numeric’ function.

Round Date/Time
• Round
• Ceiling
• Floor

Round to Week
Now timestamp column shows each week’s start date

Round to Month
Now timestamp column shows each month’s start date (i.e. 1st)

# round
round_date(start_time, unit="week")
# ceil
ceiling_date(start_time, unit="week")
# ﬂoor
ﬂoor_date(start_time, unit="week")
Round vs. Ceiling vs. Floor

round_date(ymd(“2017-06-24”), unit="week")
→ “2017-06-25"
Round

The border is on Wednesday noon
Round

ceiling_date(ymd(“2017-06-24”), unit="week")
→ “2017-06-25"
Ceiling

The border is on Sunday midnight (0:00am)
Ceiling

ﬂoor_date(ymd(“2017-06-24”), unit="week")
→ “2017-06-18"
Floor

The border is on Sunday midnight (0:00am)
Floor

To round date to week..
1. Select “Round”
2. Select “Round Date ”
3. Select “Week”

round_date(created_at, “week”)

• We have Temperature Data of London and Tokyo
• Each row represents a temperature for a certain date/time in year 2016.
There are 17,498 temperature data of London and 19,489��temperature
data of Tokyo
• Each temperature record has date/time, longitude, latitude, temperature,
etc
• Filename: Date-London-temp.csv and Date-Tokyo-temp.csv
Timezone - Data

For London, 2:00pm is the peak of
Average temperature
→ It sounds reasonable.
For Tokyo, 5:00am is the peak of
Average temperature
→ ???
When you compare hourly temperature data
between London and Tokyo
Data: Date-London-temp.csv, Date-Tokyo-temp.csv

• From the hourly temperature data of Tokyo, I want to know what time is
the most hot in the day, but the time indicated by the date / time data
is different from the actual time in Tokyo
• We would like to compare average hourly temperatures of two cities
with different time zones
Problem

2PM JST (Japan Standard Time)
2PM GMT (Greenwich Mean Time)
Timezone

London Tokyo (Time difference from London: 9hours)

UTC (Coordinated Universal Time)
• It is the base point for all other time zones in the world
• POSIXct is basically based on the UTC
• UTC and GMT (Greenwich Mean Time) are almost identical. (→ That is
why the hourly temperature data for London is displayed correctly on
the previous chart.)

Timezone
• 2017-01-01 08:10:10 UTC
• 2017-01-01 08:10:10 -900

Various Time zones
• America/New York
• America/Los_Angeles
• Asia/Tokyo

Asia/TokyoAmerica/Los_Angeles America/New_York

with_tz
# Append Timezone information
with_tz(ymd_hms("2015-10-01 02:20:34”))
→ "2015-09-30 19:20:34 PDT"
Default value of with_tz is local
machine’s timezone.
In this example, PDT (Paciﬁc
Daylight Time)

with_tz(ymd_hms("2015-10-01 02:20:34”))
→ "2015-09-30 19:20:34 PDT"
with_tz(ymd_hms("2015-10-01 02:20:34"), tz = "Asia/Tokyo")
→ "2015-10-01 11:20:34 JST"
with_tz
By specifying timezone information,
You can convert date/time to any
timezone

with_tz
1. Select “Create Calculation”

lubridate
Do more with dates and times in R
https://lubridate.tidyverse.org
Garrett Grolemund Hadley Wickham Vitalie Spinu

January 15th (Tuesday), 2019
• Data Wrangling: Working with Text Data
Planned
• Analytics 101 - When to use which algorithms?
• Data Wrangling: Introduction to Regular Expression
https://exploratory.io/online-seminar

Contact
Email
kan@exploratory.io
Data Science Training
https://exploratory.io/training
Twitter
@KanAugust
Online Seminar
https://exploratory.io/online-seminar

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Data Wrangling: Working with Date / Time Data and Visualizing It

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