Category Archives: Chart Principles

Basic principles for effective charts, drawing on guidance from Tufte, Cleveland, Robbins, Few.

Tracking JAXA Arctic Sea Ice Extent Trends

See my Arctic Update Page for daily updates on Arctic Sea Ice Extent

Arctic Sea Ice Extent (SIE) follows an annual cycle, with maximum levels usually in March and minimum values in September.  Many analysts use day-of-year charts to compare the SIE cycle by years so that they can assess the current years trend with previous years. In this post, I present an alternative to the day-of-year chart which shows the daily values a calendar month previous years and the current year.

Arctic Sea Ice Extent (SIE)

I have discussed Arctic Sea Ice Extent (SIE) here and here. Both of those posts used the NSDIC monthly Arctic SIE data. In this post, I use the Japan Aerospace Exploration Agency (JAXA) daily data series, available at this link.

Here’s the JAXA day-of-year chart . Click image to enlarge.

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Tracking Long Term and Recent UAH Channel 5 Anomally Trends

In this post I present  combined long term and recent trend charts of UAH Channel 5 temperature anomalies using R’s figure inside figure capability.  This approach provides a better picture of global temperature trends than UAH’s day-of-year plots.

Introduction

The University of Alabama Huntsville (UAH) provides a daily update to their Channel 5 global average temperature at 14,000 feet. I have previously posted about this data set here. The source data file link is here.

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Visualizing Arctic Sea Ice Extent Trends

Reader GH sent me an e-mail asking about a previous Arctic sea ice extent trend post (click). GH asked ….

“Why is there such a difference between this type of representation and the chart at link ? What you’ve written above seems to imply that the definitions of extent are the same.   Just looking at 2002 – present,  I’m not clear why the JAXA chart doesn’t appear to demonstrate the same clear trend. ..”

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Chart Doctor Update

Non Issue Is Over

It’s been an interesting 24 hours  in the chart blog world. I am happy to announce that the Chart Doctor name issue is completely resolved on my part and I apologize for generating what turned out to be an unnecessary controversy because Akismet flagged my comment to Chandoo’s post as spam. Continue reading

The Original Chart Doctor

Chart Doctor Started 9/30/06

I started my Chart Doctor feature at ProcessTrends.Com way back on 9/30/06: Continue reading

Don’t Try This With Excel

In this post I show 4 charts of the same data to demonstrate  what Excel chart users are missing by not having a more powerful charting tool. This post,  building on my previous discussion of using factors for conditional formatting,  shows the potential advantages of plotting summary values and bounding area polygons . These analytical displays are not readily available to even advanced Excel users. Continue reading

Excel Deja Vu All Over Again

In reading a recent Excel charting post, I got that Yogi Berra feeling, “..this is deja vu all over again”. I could have sworn that I had made or seen  a similar chart several years ago. This  post looks into the deja vu mystery and reports on my findings. You’ll have to read this post to see if Yogi’s quote applies to Excel charts.

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Temperature Anomaly Data Displays

Is there a single “best” way to display temperature anomaly data? The answer is obvious – NO! The best display depends on what we are trying to show.  Statistical charts compare one variable with one or more other variables.

Since our display option affects how we interpret the data, it is important to be clear on what we are comparing. In this post I want to show 3 ways to display temperature anomaly data and the implications that the display method has on our interpretation of the data. I’ll use a map, a trend chart and a dot plot. Continue reading

Showing Change Points in a Trend Chart with R

In this post, I show how to add change points to a trend chart with R. Readers can compare my R and Excel – VBA solutions for the same chart to compare R and Excel VBA charting programming. Continue reading

Boxplots: R Does Them Right

In this post, I define a Tukey boxplot, review the history of boxplots in Excel and walk through an R script for making a proper Tukey boxplot. A link to the source data and R script files is provided. Continue reading