Charts and Graphs Skills Review

Part of the SAS Accessibility Team recently taught this activity with students in the SAVVY Transition Program in North Carolina. This post is follows the written lesson plan which is available on the SAS website, Introduction to Data Analysis Using SAS Graphics Accelerator - Instructors Materials. This activity was created and led by two SAS interns and a recent grad who is a full time SAS employee; all three men are visually impaired. The college-bound SAVVY students are rising high school seniors or incoming college freshmen; all are visually impaired.

Charts and graph skills are challenging for many students who are visually impaired. Informal studies and observations have strongly indicated that many braille and low vision students have gaps in their skills or lack the skills to systematically explore a chart and to quickly glean specific information from the chart. Students need to be exposed to a variety of charts (line, bar, pie, series, scatter plot, etc.), have a general understanding of the layout of each chart type and understand what each type of chart is used for before diving into the data the chart provides.

Example charts used in this post are available on the SAS website. The charts can be embossed, printed and accessed auditorily. If necessary, guide the student to systematically explore each chart. Ask pertinent questions about the chart's basic information and then about specific data information to confirm that the student understands each chart. (See the SAS lesson plan for suggestions.) Four chart types will be used in this activity: bar chart, line chart, pie chart and series plot.

Note: When embossing charts directly from SAS Graphics Accelerator, currently braille labels are not available - only the tactile graphics of the chart are embossed. Braille labels should be added manually.

Begin the activity by exploring the tactile or printed charts.

Basic Chart Information

Students should be systematically be taught to identify the title of the chart, type of chart, what the X and Y-axis represent and if appropriate, the range, before exploring the data points or content of the chart.

Terms 

  • Chart: A graphical or visual representation of data. 
  • Y-Axis: A line on a graph that runs vertically (up-down)
  • X-Axis: A line on a graph that runs horizontally (left - right)
  • Bar Chart: A graphical display of data using bars of different heights where the length of the bar is proportional to the data value
  • Line Chart: A type of chart which connects individual data points that, typically, display quantitive values over a specified time interval
  • Pie Chart: A graph in which a circle is divided into slices to illustrate relative sizes of the data set
  • Series Plot: A graph which displays values against time
  • Trend: A general direction in which a group of points seem to follow (Examples: Increase, decrease, spike, dip, flat line, jagged)

Tactile/Print Charts

Bar Charts

A bar chart (also known as a bar graph) is a graphical display of data using bars of different heights where the length of the bar is proportional to the data value. Bar charts are categorical with the Y-axis typically depicting a measured value of the categories being compared.

Students using bar charts in braille format should track the bar to the top of the bar and then trace the lighter grid lines to the left to find the number on the Y-axis. If the bar falls between two grid lines, the student should trace the closest grid line and estimate the value based on the bar's height, which will fall between the closest two numbers.

Simple bar charts are typically introduced to students first and are incorporated into the kindergarten curriculum. The bar chart below is called "Bar Chart Showing Gravity". The Y-axis shows the gravity ranging 0 - 80 in increments of 20. The X-axis depicts the planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.

Note: Pluto is no longer considered a planet.

Bar Chart showing gravity by planet

The Bar Chart Showing Gravity is available on the SAS website.

Line Chart

A line chart (also known as a line plot or line graph), is a type of chart which connects individual data points that, typically, display quantitive values over a specified time interval. Line charts may lose clarity when there are too many data points.

Note: A line chart may or may not show visually/tactually show specific dots (data points) on the line; but, the points are implied and can be determined. The line chart used in this example (Sample #1) does not show specific dots; however, when using the accessible audio version, the user can move point by point and the values of each point can be announced.

The next two images are of the same Sample #1 Line Chart. The first image is the visual line chart which shows a straight line running diagonally from the lower left to the upper right. The line starts at 1,1 and ends at 35,35. The Y-axis ranges from 0 - 35 (no label on the Y-axis) and the X-axis also ranges from 0 - 35. Increments are in tens.

Sample #1 Visual line chart.

The second version of the Sample #1 chart is the SAS Graphics Accelerator version - the auditory version for students who are visually impaired. In the auditory version, only one data point can be shown at a time. In this image, the data point X = 8 and Y = 8 is shown. To assist low vision users, the data point is displayed as a larger square and the entire column is outlined. Outside and to the right of the chart in print is, "X = 8" and "Y = 8". Students can navigate through the chart by individual points using the right or left arrows or can navigate through the entire chart using additional commands.

Note: The auditory version of the chart is provided now for informational purposes for the teacher only, as the initial chart activity is to review the chart skills using the tactile or print versions of the chart.

Sample #1 Auditory version of the same Line Chart

The Sample #1 Line Chart is available on the SAS website.

Briefly take a look at the other three Sample line charts. Discuss how to determine a trend (general direction in which a group of points seem to follow) and what the trend is for each chart. 

Pie Chart

A pie chart is a graph in which a circle is divided into slices to illustrate relative sizes of the data set. Pie charts are used to compare the sizes (proportions) of each data set. All the slices added together will equal 100%.

With this SAS braille pie chart, the circle is covered in random dots with the absence of dots providing the dividing lines between slices. Some tactile pie charts will use different textures or different braille patterns to indicate the different slices. Braille students should learn to trace the outer edge of the circle in order to explore and compare the sizes of the different slices.

The first image below shows the colorful donut-shaped pie chart showing percent volume by gas for Earth's atmosphere. This version shows Nitrogen 78,060 percent, Oxygen 20.950% and Other .975%. The second image shows the black and white printed circle of the same pie chart but does not include the written percentages. Note: The corresponding braille version matches the black and white version without braille labels. (Braille labels should be added after the image is embossed.)

Visual pie chart showing Percent volume by Gas for Earth's atmosphere on SAS website.

Black and white version of the Pie chart showing percent volume by Gas for Earth's Atmosphere.

The Pie Chart showing Percent Volume by Gas for Earth's Atmosphere is available on the SAS website.

Series Plot

A series plot (also known as a series chart or time plot), displays values against time. It is a specific type of line chart where the x-axis is always time and is used for showing how data changes over time. A series plot typically has numerous data points creating a jagged-looking line. A good example of a series plot is data gleaned from a heart monitor.

The series plot below shows the Relative Temperature by Year. The Y-axis depicts the relative temperature ranging from -0.5 to 1.0 in .5 increments. The X-axis is in 25 year increments ranging from 1875 - 2025. (Note: the data points start at approximately 1878 and stop at approximately 2019. The graph has a jagged line with a rising trend.

Series plot showing Relative Temperature by Year.

The Series Plot Showing Relative Temperature by Year is available on the SAS website.

Accessible Digital Charts

Once the student understands the basic types of charts using tactile, print or large print materials, then introduce accessible digital charts, including sonification.

Learn more about sonification with Sonification: Sounds have Meaning Activity post.

These activities require a computer (PC or Mac), Google Chrome, stereo headphones/ear buds/speakers and the free SAS Graphics Accelerator application. SAS Graphics Accelerator (Accelerator) is fully compatible with screen readers.

Sonification can make digital charts accessible for students who are visually impaired. Sonification is simply using sound to communicate information. The Y-axis uses pitch: data points that are higher on the graph have a higher pitch and data points that are lower on the graph have corresponding lower pitch. The X-axis pans the sounds from the left to the right - data points on the left side of the chart will be heard in the left ear, data points in the center of the chart will be heard in both ears, and data points on the right side of the chart will be heard in the right ear.

Note: Stereo headphones/ear buds stereo speakers (set up on the left and right sides) must be used in order to hear the panning sounds. Be sure that the speakers/headphones are adjusted so that the sounds on the left reach the left ear and the sounds on the right reach the right ear.

The charts mentioned above will now be used in their accessible digital format. 

On your computer using Google Chrome, open the Sample Chart Link. This link opens a page with four sample line charts. In the bottom right corner below of each chart is an Accelerate button. Select the Accelerate button for the first chart.

Note: The Accelerate button is only available in the Google Chrome web browser. If you opened the link in another browser, the Accelerate button is not there.

Note: Once you install SAS Graphics Accererator, you will have a small blue "s" symbol (SAS Graphics Accelerator icon) in the Google Chrome tool bar to the right of the URL field. This indicates that the Accelerator is available, enabling users to download compatible charts from the Internet. 

The screenshot below shows the Sample page with four Sample line charts. Sample #1 has a red annotated arrow pointing to the Accelerator button below that chart in the bottom right corner. Another red annotated arrow points to the small blue "s" - the Accelerator icon - in the Google Chrome tool bar. Sample #1 is a straight line moving from the bottom left to the top right. Sample #2 is a straight line moving from top left to the bottom right. Sample #3 starts at the top left, curves to the bottom and back up to the top right. Sample #4 is a wavy line (two humps and two dips) across the middle of the screen starting at 20.

Screenshot of the Sample Line Chart page with annotated arrows pointing to the Accelerate button in Sample 1 and the SAS icon in the tool bar.
The Sample line charts are available on the SAS website.
 

Selecting the Accelerate button will open the Sample chart in the SAS Graphics Accelerator. 

Note: Teachers, explore the Accelerator before introducing it to students. The instructions below will introduce the Accelerator features required for exploring these graphics in this activity.

Using the Accelerator Without a Screen Reader (Teacher)

For teachers who are not familiar with a screen reader, press the right or left arrow key to move data point by data point. Be sure to listen to the pitch of each data point. When the screen reader is off, the points are not announced but are shown visually on the screen. Explore the data points at your own speed, moving forward and backward through Sample #1.

The Accerator's default mode is is in the Explore mode, meaning that using the right arrow will move by individual data points to the right. There are various Settings options. Select the Settings button in the top left above the chart.

Settings Options

  • Sound
  • Speech
  • Speed 
  • Navigation

Sound: On/off sound (default is On)

Speech: Terse, Verbose, Off (terse means brief announcements, verbose is more chatty and Off is no announcements; default is Terse)

Speed: Slowest, Slow, Normal, Fast, Fastest (When in Scan mode, Speed determines how fast the Accelerator will scan/play the notes; default is Slow to introduce new users to sonification)

Navigation: Explore (user controls which data point will be played/announced) or Scan (one command will play all the notes/announcements)

After exploring individual notes, change the Navigation setting to Scan mode. Now, press the right arrow one time. The Accelerator will automatically play through all the notes - one at a time - across the chart. Speed up the scanning mode by selecting Speed > Fast or Faster. Try slowing down the speed in order to comprehend individual points of data.

Pay attention to the pitch of the data points; the pitch represents the Y-axis. Which data point is the highest pitch? Lowest pitch? Pay attention to the where the note is located (left ear, both ears, right ear). When starting from the first note (left side of the chart) and moving across the chart, the sound will move from your left ear, to both ears, to the right ear - this represents the X-axis. (Note: Stereo headphones, earbuds or speakers are required!)

Using the Accelerator With a Screen Reader (Teacher)

The Accelerator is designed to be fully compatible with a screen reader. The Settings button can be used and/or the screen reader user can use a number of additional keyboard commands. To view the full list of keyboard commands, open the Help button which is located beside the Settings button above the chart on the left side.

Note: For users who are not familiar with using a screen reader, it is possible to turn on your screen reader and still use your mouse if needed in order to try out these keyboard commands. If unfamiliar with a screen reader, I suggest opening the desired chart first, then turn on your screen reader. Use your mouse to move the screen reader focus between the chart and Help button. Place the screen reader cursor on the chart and practice the main keyboard commands. 

Hint: If using VoiceOver on a Mac, Command F5 then hold Control + Option and F8 to turn on VoiceOver. Press Control + Option and F8 quickly so that you do not have to listen to the VoiceOver instructions that begin when you press Command F5.

Educators who are familiar with a screen reader can quickly explore the Help menu to learn the Accelerator features and commands.

Sonification Activity

Once you - the educator - have explored the chart using the Accelerator and have become familiar with the sonified charts, the next step is to introduce your student to sonification. You - the educator - should demonstrate sonification - students should only listen in this activity. Sonfication is beneficial for students who rely on screen readers, magnification/zoom and print. Sighted students can quickly glance at a visual chart and instantly determine the trend. One of the "super powers" of using sonification is the ability to quickly "glance" (listen) and instantly determine the trend.

This sonification activity is done after reviewing the tactile/print charts. Have the physical charts available on the desk in front of your student. Ask your student to listen carefully to the Bar Chart Showing Gravity that you have open in the Accelerator. For this activity, the title and labels of the chart are not important - the goal is to listen and learn about sonification. In Scan mode and Fast speed, play the bar chart. Slow the speed and play again. Ask the students to describe what they heard. Discuss that pitch corresponds to the Y-axis and panning corresponds to the X-axis. Play it again. What stands out in the sonified chart?  Change to Explore mode and navigate one data point at a time - feel free to move forward or backwards. Is there one note that is higher than the others? Where is that note located (both ears - middle of chart). Is there one note that is lower than the others? Where is that note located (right ear - end of chart). What is the over all trend? (Spike in the middle of the chart.)

Accelerate and Use Sample #1. Use the Scan mode, Fast or Faster speed. Ask the student to describe what they hear and then explain what that means. (Example: Sounds start low in the left ear and systematically increase pitch while moving to the right ear. This indicates a trend that increases.) Now ask the students to pick the tactile/print version chart that corresponds with the chart that just heard.

Repeat the activity with the four Sample line charts. Then demonstrate the series chart which is more complex with it's numerous data points. After scanning the series chart in fast or faster mode, slow down the speed to help students listen and better comprehend this complex chart.

Note: It is best to demonstrate the sonification without using a screen reader, as the screen reader will announce the title of the chart!

Resources

SAS Graphics Accelerator Posts

The next post in this series builds on and applies the charts used in this post. 

There are a number of additional Accelerator posts; here are a few to help you get started!

Download Images

Download the the following 4 graphs used in these activities in .png images:

Collage of charts and graphs skills