Case Study: Venus Plasma Data

This data set consists of 8784 data points acquired over 1 month (Jan. 92) from the Pioneer Venus Orbiter. 7 parameters are examined: Date, hour, latitude, longitude, plasma velocity, plasma density, and plasma temperature. It was obtained in ASCII format via NSSDC COHOWeb and converted to XmdvTool format.

High Plasma Temperature

This image shows a parallel coordinates view of the data, with a brush formed by dragging over the region with high plasma temperature data. As can be seen, this data occurred over a small number of days, and has corresponding low values for plasma density.

Statistics on Individual Parameters

This image shows a modified Tukey Box Plot for each dimension. The red circle shows the median value, the red box shows the outline for the middle 2 quartiles, the red dashed lines shows the points within 1.5 times the 25-75 quartile range of the median, and red dots indicate outliers. The blue circle shows the mean value and the blue angle brackets show the standard deviation. Missing data points (represented by values such as 999.999 within the data set) have been filtered out by the brush. The data count shows that nearly 5/6 of the 8784 points have missing values.

Temporal and Spatial Distribution of Missing Data

This scatterplot matrix shows (in red) the valid data and (in green) the data with missing parameters. The Date/Hour plot shows the time period of the gaps, while the Longitude/Latitude plot shows the region of the missing data.

Matthew O. Ward (