Your First Plot

Learn how to create beautiful, interactive plots with VSL in just a few lines of code.

What You'll Learn

• Creating your first scatter plot
• Understanding the VSL plot API
• Customizing plot appearance
• Generating and visualizing data

Prerequisites

• VSL installed (see installation guide)
• Basic V language knowledge

Theory

VSL's plotting module provides a Plotly-inspired API for creating interactive visualizations. Plots are created by:

1. Creating a Plot object
2. Adding traces (data series)
3. Configuring layout
4. Displaying the plot

Basic Scatter Plot

Let's create a simple scatter plot:

import vsl.plot
import vsl.util

fn main() {
	// Generate data: x from 0 to 10, y = x²
	x := util.arange(11).map(f64(it))
	y := x.map(it * it)

	// Create plot
	mut plt := plot.Plot.new()

	// Add scatter trace
	plt.scatter(
		x:    x
		y:    y
		mode: 'lines+markers'
		name: 'Quadratic Function'
	)

	// Configure layout
	plt.layout(
		title: 'My First VSL Plot'
		xaxis: plot.Axis{
			title: plot.AxisTitle{
				text: 'X values'
			}
		}
		yaxis: plot.Axis{
			title: plot.AxisTitle{
				text: 'Y values'
			}
		}
	)

	// Display plot
	plt.show()!
}

Save this as first_plot.v and run:

v run first_plot.v

An interactive HTML plot should open in your browser!

Understanding the Code

Data Generation

import vsl.util

x := util.arange(11).map(f64(it))  // [0, 1, 2, ..., 10]
y := x.map(it * it)                 // [0, 1, 4, ..., 100]

util.arange(n) creates an array [0, 1, 2, ..., n-1]. We convert to f64 and map to create y-values.

Creating the Plot

import vsl.plot
import vsl.util

mut plt := plot.Plot.new()
x := util.arange(11).map(f64(it)) // [0, 1, 2, ..., 10]

Creates a new plot object. The mut keyword allows modification.

Adding Traces

import vsl.plot

mut plt := plot.Plot.new()
x := []f64{}  // Assume populated
y := []f64{}  // Assume populated
plt.scatter(x: x, y: y, mode: 'lines+markers', name: 'Quadratic Function')

Adds a scatter trace with:

• x, y: Data arrays
• mode: How to display ('markers', 'lines', or 'lines+markers')
• name: Legend label

Layout Configuration

import vsl.plot

mut plt := plot.Plot.new()
plt.layout(
    title: 'My First VSL Plot'
    xaxis: plot.Axis{title: plot.AxisTitle{text: 'X values'}}
    yaxis: plot.Axis{title: plot.AxisTitle{text: 'Y values'}}
)

Configures plot appearance: title, axis labels, etc.

Displaying

import vsl.plot

mut plt := plot.Plot.new()
plt.show()!

Opens the plot in your default browser. The ! indicates this can fail.

Customizing Appearance

Colors and Markers

import vsl.plot

mut plt := plot.Plot.new()
x := []f64{}  // Assume populated
y := []f64{}  // Assume populated
plt.scatter(
    x: x
    y: y
    mode: 'markers'
    marker: plot.Marker{
        size: []f64{len: x.len, init: 10.0}
        color: []string{len: x.len, init: '#FF5733'}
    }
)

Multiple Traces

import vsl.plot
import vsl.util

x := util.arange(11).map(f64(it))
y1 := x.map(it * it)           // x²
y2 := x.map(it * it * it)      // x³

mut plt := plot.Plot.new()
plt.scatter(x: x, y: y1, name: 'Quadratic')
plt.scatter(x: x, y: y2, name: 'Cubic')
plt.layout(title: 'Multiple Functions')
plt.show()!

Exercises

1. Modify the function: Change y = x² to y = sin(x) or y = 2x + 1
2. Add more traces: Plot multiple functions on the same plot
3. Change colors: Use different colors for each trace
4. Adjust markers: Change size, shape, or style

Common Plot Types

Line Chart

import vsl.plot

mut plt := plot.Plot.new()
x := []f64{}  // Assume populated
y := []f64{}  // Assume populated
plt.line(x: x, y: y, mode: 'lines')

Bar Chart

import vsl.plot

mut plt := plot.Plot.new()
categories := []string{}  // Assume populated
values := []f64{}  // Assume populated
plt.bar(x: categories, y: values)

Histogram

import vsl.plot

mut plt := plot.Plot.new()
data := []f64{}  // Assume populated
plt.histogram(x: data)

Next Steps

• Basic Linear Algebra - Work with matrices
• 2D Plotting Tutorial - Advanced plotting
• Examples Directory - More plot examples

Related Examples

• examples/plot_scatter - Scatter plot example
• examples/plot_line_axis_titles - Line charts with labels
• examples/plot_bar - Bar chart example
• examples/plot_histogram - Histogram example