Supercharge Your Data Visualization: A Gnuplot Pie Chart Tutorial with Enhanced Highlighting

Want to make your data pop? Gnuplot can create stunning pie charts, but highlighting specific sections can be tricky. This guide provides a refined Gnuplot script for creating impactful pie charts, focusing on how to highlight a specific section with both color and patterns. This is especially useful when you need to visually emphasize key data points in your data visualization project.

Problem: Highlighting a Pie Chart Slice

Sometimes, a simple color fill isn't enough. You might need to make a particular slice really stand out. This article will show you how to combine color and patterns in Gnuplot to achieve this.

Solution: Combining Color and Patterns in Gnuplot

The following script generates two pie charts side-by-side, visualizing data before and after a lecture. The key improvement lies in how the second pie chart highlights a specific segment ("Q5C_a") using both a green background and black diagonal lines. Let's break down the critical parts.

reset
set terminal pngcairo size 1000,500 enhanced font 'Arial,14'
set output 'ATU20250410_Piechart_Q5.png'
set multiplot layout 1,2 title "Q5: Hvordan maales den samlede masse af en galaksehob?"
unset key
unset border
unset tics
set size square
set xrange [-1:1]
set yrange [-1:1]
set angle degrees

#Pie Chart 1: BEFORE
set title "Before Lecture"
unset object
unset label

set object 1 circle at 0,0 size 1 arc [0:280] fillstyle solid 1.0 fillcolor rgb "orange"
set object 2 circle at 0,0 size 1 arc [280:360] fillstyle solid 1.0 fillcolor rgb "green"

set label 1 "Q5F: 7" at -0.5, 0.8
set label 2 "Q5C (correct answer): 2" at 0.4, -0.6
plot [-1:1][-1:1] 1/0 notitle

#Pie Chart 2: AFTER
set title "After Lecture"
unset object
unset label

angle_b = 0
angle_c = angle_b + 154
angle_f = angle_c + 154
angle_a = angle_f + 26

set object 3 circle at 0,0 size 1 arc [angle_b:angle_c] fillstyle solid 1.0 fillcolor rgb "green"

# Key steps for highlighting:
set object 4 circle at 0,0 size 0.999 arc [angle_c:angle_f] fillstyle solid 1.0 fillcolor rgb "green" # Base green color
set object 7 circle at 0,0 size 1 arc [angle_c:angle_f] fillstyle pattern 6 # Pattern overlay

set object 5 circle at 0,0 size 1 arc [angle_f:angle_a] fillstyle solid 1.0 fillcolor rgb "orange"
set object 6 circle at 0,0 size 1 arc [angle_a:360] fillstyle solid 1.0 fillcolor rgb "purple"

set label 3 "Q5B (correct answer): 6" at -0.8, -0.5
set label 4 "Q5C (correct answer): 6" at -0.8, 0.6
set label 5 "Q5F: 1" at 0.35, -0.4
set label 6 "Q5A: 1" at 0.35, -0.1
plot [-1:1][-1:1] 1/0 notitle

unset multiplot

Key Enhancements Explained

• fillstyle pattern 6: This is where the magic happens. pattern 6 specifies black diagonal lines. You can experiment with other pattern numbers (1-12) for different effects.
• Layering for Effect: First, we create a slightly smaller green slice (object 4). Then, we overlay a patterned slice with a full radius (object 7). This ensures the pattern sits cleanly on top of the color.

Actionable Insights

• Experiment with Patterns: Gnuplot offers a variety of fill patterns. Consult the Gnuplot documentation to find one that suits your needs.
• Adjust Transparency: For subtle highlighting, use transparent fill colors in conjunction with patterns.
• Customize Labels: Clearly label each slice with relevant data and descriptions for better understanding.

Level Up Your Gnuplot Pie Charts

By using this technique you will be able to effectively use the gnuplot pie chart function and make your data stories more compelling than ever. With this gnuplot highlight trick, you can draw instant attention to critical segments. And if you need even more space for detail, explore making a data visualization project with longer, informative label text!