Upload
phungthuy
View
222
Download
2
Embed Size (px)
Citation preview
Week 4LSP 120
Joanna Deszcz
3 Types of Graphs used in QR Pie Charts
Very limited useCategory sets must make a whole
XY Graphs or Line GraphsUse with “a lot” of data points
Bar Charts or Column ChartsVery flexibleWork well with limited data Compares more than one series
Pie Charts Only used when have
a quantitative variable associated with a list of categories
Both the categories and the quantities each add up to a whole
Categories must be disjoint – no overlapping
Most Common Pie Chart Mistakes Use on set of categories that don’t make
a whole Use on categories that overlap Include total in chart data
Let’s try an exampleLeading Causes Of Death Tab
Creating a Pie Chart Select labels and
values Choose Pie chart type Choose layout
Must include % value, title and labels
Layout 6 does it all Add the source in a
text box
Labeling the Chart Title should be descriptive
Consider who, what, when and where Percents should be formatted to 2
decimal placesFormat – Data Labels – Numbers –
Percentage – 2 decimal places Source – add in text box
Insert – Text Box – Draw text box on the chart and type in source
If not source give type “Unknown”
Chart Themes Found on Page Layout Tab Slide mouse over built-in themes
Chart will change to reflect each theme
The Result…
Flow Theme applied to the chart
XY Graphs Used with a lot of
data X-axis categories
are numeric, (often years)
Choose xy graph option with connected data points
Note: Don’t use the Line Graph Excel line graphs always treat the x-axis
categorically instead of numerically
Causes endless array of mistakes
Use XY (Scatter) graph instead to avoid errors
Let’s try one Lake Michigan Levels Tab
Creating XY (Line) Graphs Select category
labels and values Choose Scatter
chart optionScatter with straight
lines and markers type
2nd row, 2nd column Choose design
layout 1 from Design tab
Labeling the Chart Title should be descriptive
Consider who, what, when and where Remove the legend from the chart
Not needed when there is only one series Source – add in text box
Insert – Text Box – Draw text box on the chart and type in source
If not source give type “Unknown” Apply a theme if you wish
Make Your Chart More Readable XY Graphs often only
take up a small range of values
If all data points located in a central area on the graphAdjust y-axis so
values start at or just below the lowest data point value
•Right-click on y-axis•Choose Format axis•Adjust Minimum value
The Result…
Solstice Theme applied to this chart
What’s the Story? XY (Line) Graphs usually tell a story about the data
Analysis should carefully describe what the graph is saying
Start the “story” from the left and move to the right
Be sure to include the high point and the low point as well as anything that is interesting or unexpected
Write a well-written paragraph telling the “story”
Describing your graph In a paragraph, point out what you want the
reader to know about the graph Examples:
“In the Annual Averages of Lake Michigan/Lake Huron Water Levels chart we find that between 1988 and 1997 water levels in the lakes increased overall. The high point of the lake levels occurred in 1997 when the level was 176.98 meters. However, lake levels took a sharp decline in the following 2 years and reached their low point in 2003 when the level was only 175.89 meters. Since 2003 lake levels have increased slightly but appear to be declining once again.”
Bar Chart or Column Chart Very flexible Used when a
quantitative variable is associated with the a categorical variable
Work well with limited data
Can compare more than one series
Note: Be Careful If you do use a bar chart and have years
along the x-axis Be sure the years are in equal intervals. Otherwise, you can be guilty of creating
a misleading graph
Let’s try one Home Heating Tab
Creating a Column Chart Select the data
including category labels and values
Choose Column Chart2-D Clustered column
option Add Titles and axis
labelsLayout 9 works well
Labeling the Chart Title should be descriptive
Consider who, what, when and where Both the x-axis and y-axis should be
labeled Source – add in text box
Insert – Text Box – Draw text box on the chart and type in source
If not source give type “Unknown” Apply a theme if you wish
Name Each Series in the legend To change names
Click on chart to activate
Click on Design TabUnder Data Group –
choose Select DataData Series labels
appear on leftHighlight label and
click edit button Type new series
name in Edit Series Dialog box
The Result…
Aspect Theme applied to chart
Source: US Dept of Energy
Add the other column of data Reselect the data to include all 3
columns
The New Result
Source: US Dept. of Energy
Advantages of Multiple Bar Charts Succinctness Can make comparisons within
categories and across categories Best used in printed works
Can be carefully studied
Disadvantages Can present too much information to
view as part of presentation Hard to make a single clear point with
bar charts Presenters don’t leave them up long
enough to absorb info fully
Describing a Bar/Column Chart Usually include high and low values in
graph description Not always effective/appropriate with
bar/column charts Include top 2 or 3 values instead Low value may be insignificant
Often describes “Other” categoryNot significant in the “story”
Guidelines for Creating an Effective Graph1. What is the purpose of making a graph
from this data?
2. What type of graph should you make? Pie, bar, x-y scatter (line)
3. Decide on a title and consider the W's (who, what, where and when)
4. Do you need to include a legend?
Guideline continued…5. Add a descriptive x-axis and y-axis label
for bar and xy-scatter graphs
6. Add percentages for pie charts, 2 decimal places
7. Adjust the scale for bar and xy-scatter graphs (if applicable)
8. Add source
Can the Graph Stand Alone? A good graph should be able to stand
alone Without any words to tell the reader what
they are looking at
If the reader doesn't understand the graph without a caption (or story) then the graph isn't very good
Faulty or Misleading Graphs Data can be displayed "correctly" yet
gives different messages depending on how it is displayed
Y-axis Scale Effects Most common way to create a
misleading graph Y-axis scale should begin at 0 Not always the case Can work in favor of the one distributing
the graph
Bad Chart Examples What’s wrong with this chart
Another Bad Example – Misleading Graph
Graph appeared in Chicago Tribune and on billboards along the Kennedy Expressway