data-import.qmd

---
title: "Data Import"
---

## Introduction

### Prerequisites

In Julia, you can read data from CSV files using the `CSV.jl` package, which provides functionality to handle CSV files efficiently.

```{julia}
using Tidier, CSV
```

## Reading data from a file

```{julia}
df = CSV.File("df.csv") |> DataFrame
```

### Handling different delimiters

```{julia}
df = CSV.File("df.csv", delim = ";") |> DataFrame
```

### Handling missing values

```{julia}
df = CSV.File("df.csv", missingstrings="N/A") |> DataFrame
```

### Specifying column types

```{julia}
df = CSV.File("df.csv", types=Dict(:Age => String)) |> DataFrame
```

## Writing data to a file

```{julia}
df = DataFrame(Name=["Alice", "Bob", "Charlie"], Age=[25, 30, 35], Country=["US", "UK", "Canada"])

CSV.write("df.csv", df)
```

### Specifying delimiters

```{julia}
CSV.write("df.csv", df, delim=';')
```

### Specifying missing values

```{julia}
CSV.write("df.csv", df, missingstring="N/A")
```

### Writing a subset of columns

```{julia}
CSV.write("df.csv", df, cols=[:Name, :Age])
```

## Reading data from other sources

### Excel Workbooks

```{julia}
#| eval: false
using XLSX
```

### Google Sheets

```{julia}
#| eval: false
using GoogleSheets
```

### SQL Databases

Many options actually: [https://juliapackages.com/c/database](https://juliapackages.com/c/database)

### Arrow

```{julia}
#| eval: false
using Arrow
```

### Hierarchical Data

```{julia}
#| eval: false
using JSON
```

### Web scraping

```{julia}
#| eval: false
using TidierVest
```