STA 326 2.0 Programming and Data Analysis with R

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# STA 326 2.0 Programming and Data Analysis with R
## 🌍 Data Import and Export
### 
### Dr Thiyanga Talagala

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# Today's menu

.pull-left[

- Data import

- Data export

]

.pull-right[
<center><img src="importcover.jpeg" height="500px"/></center>
]

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background-image: url(readr.png)
background-size: 100px
background-position: 98% 6%

# Data Science Workflow: Import

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## Data import with readr

`readr`: part of the core tidyverse.

```r
library(tidyverse)
```

## `readr` data import functions

- `read_csv`: reads comma-delimited files.

- `read_csv2`: reads semicolon-separated files

- `read_tsv`: reads tab-delimited files

---

## 🛠 Import data from a .csv file (local machine)

### Syntax

```r
datasetname <- read_csv("include_file_path")
```

When you run `read_csv`, it prints out the names and type of each column.

.full-width[.content-box-yellow[Switch to R]]

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## If the file is saved inside the project folder: part 1

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## If the file is saved outside the project folder: part 2

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## 🛠 Importing csv file from a website

### Syntax

```r
datasetname <- read_csv("include url here")
```

### Example

```r
url <- "https://thiyanga.netlify.app/project/datasets/foodlabel.csv"
foodlabel <- read_csv(url)
```

```r
head(foodlabel, 1)
```

```
# A tibble: 1 x 80
  Gender   Age Education Employment Income Housesize children marital fshopper
   <dbl> <dbl>     <dbl>      <dbl>  <dbl>     <dbl>    <dbl>   <dbl>    <dbl>
1      1    22         5          4      3         5        2       0        0
# … with 71 more variables: mplanner <dbl>, place <dbl>, FA <dbl>,
#   Diabetes <dbl>, Metabolic cyndrents <dbl>, Other <dbl>, specific <dbl>,
#   job1 <dbl>, job2 <dbl>, Exercise <dbl>, Health <dbl>, taste <dbl>,
#   easy <dbl>, familiarity <dbl>, friends <dbl>, Useful <dbl>, Easiness <dbl>,
#   Sufficient <dbl>, Trusfulness <dbl>, Clear <dbl>, attractive pack <dbl>,
#   hc/nutriclaims <dbl>, graphical <dbl>, Free/prize <dbl>, source <dbl>,
#   netquan <dbl>, low in fat <dbl>, low in cho <dbl>, sodium <dbl>,
#   e labels <dbl>, place2 <dbl>, fa2 <dbl>, Health_1 <dbl>, X43 <dbl>,
#   f1 <dbl>, f2 <dbl>, f3 <dbl>, f4 <dbl>, f5 <dbl>, f6 <dbl>, f7 <dbl>,
#   f8 <dbl>, f9 <dbl>, f10 <dbl>, f11 <dbl>, f12 <dbl>, f13 <dbl>, f14 <dbl>,
#   f15 <dbl>, f16 <dbl>, f17 <dbl>, f18 <dbl>, i1 <dbl>, i2 <dbl>, i3 <dbl>,
#   i4 <dbl>, i5 <dbl>, i6 <dbl>, i7 <dbl>, i8 <dbl>, i9 <dbl>, i10 <dbl>,
#   i11 <dbl>, i12 <dbl>, i13 <dbl>, i14 <dbl>, i15 <dbl>, i16 <dbl>,
#   i17 <dbl>, i18 <dbl>, cluster <dbl>
```
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## `read.csv` and `read_csv`

*  `read.csv` is in base R.

*  `read_csv` is in tidyverse.

*  `read.csv()` performs a similar job to `read_csv()`.

* `read_csv()` works well with other parts of the tidyverse.

*  `read_csv()` is faster than `read.csv()`.

*  `read_csv()` will always read variables containing text as character variable.  In contrast, the base R function `read.csv()` will, by default, convert any character variable to a factor.

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## 🛠 Writing data to a .csv file

- We can save tibble (or dataframe) to a csv file, using `write_csv()`.

- `write_csv()` is in the `readr` package.

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## Syntax

```r
write_csv(name_of_the_data_set_you_want_to_save, "path_to_write_to")
```

## Example

```r
data(iris)
# This will save inside your project folder
write_csv(iris, "iris.csv") 
# This will save inside the data folder which is inside your project folder
write_csv(iris, "data/iris.csv") 
```

Swtich to R

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# 🛠 Importing data from .xlsx files

## Syntax

```r
library(readxl)
mydata <- read_xlsx("file_path")
```

.full-width[.content-box-yellow[Switch to R]]

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# Importing SAS, SPSS and STATA files

## SAS

```r
read_sas("mtcars.sas7bdat")
write_sas(mtcars, "mtcars.sas7bdat")
```
## SPSS

```r
read_sav("mtcars.sav")
write_sav(mtcars, "mtcars.sav")

```
## Stata
```r
read_dta("mtcars.dta")
write_dta(mtcars, "mtcars.dta")
```

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# Importing other types of data

- `feather`: for sharing with Python and other languages

- `httr`: for web apis

- `jsonlite`: for JSON

- `rvest`: for web scraping

- `xml2`: for XML

.full-width[.content-box-blue[Working with feather, httr, jsonlite, rvest and xml2 is beyond the scope of the course.]]

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class: center, middle

Slides available at: hellor.netlify.app