Charts Overview

Types of Charts

You can create the following graphs from the Charts page.

• Time Series Graphs
• Histograms
• Heatmaps

Example Illustrations

To help illustrate the three types of charts, consider the graphs shown below.

Figure 1:

All three graphs show the same data—the running 1-minute average of CPU utilization on a device over the last 24 hours. However, the way the data is depicted in each illustration is different.

• The time series graph provides the typical view; every minute it adds the latest data point to the end of the line graph. Time moves forward along the x-axis from left to right, and the data values are indicated on the y-axis. However, this graph doesn’t show how often each data point has occurred.

• The histogram groups together the values to show how many of each data point there are. The tallest bar is the one between 30 and 40, which means that the most common 1-minute CPU average value is in the 30-40% range. And based on the y-axis, there have been over 350 instances of values in this range. The next most frequently occurring values are in the 40-50% range (almost 300 occurrences), while the 0-10% range has almost no occurrences, suggesting that this CPU is rarely idle. This graph doesn’t show how many instances of each data point occurred within a given time range.

• The heatmap makes use of elements from the time series graph and histogram. Each small bar indicates that some number of instances occurred within the value range shown in the y-axis, at the given time show in the x-axis. The color indicates which value ranges, for each given time, occurred more than others. The vertical set of bars towards the right of the graph, at 18:00 illustrates this. In this example (at this zoom level), each column of vertical bars represents 12 minutes, and each small bar represents a bucket of 15 values. So the first (lowest) bar indicates that within this time range there were some values in the 0-14 range. The bar above indicates that within this time range there were some values in the 15-29 range, and so on. The color indicates which bars have more values than others. In this example, the third bar is red indicating that for those 12 minutes most of the values fell into the 30-44 range (in this example the count is 21). By contrast, the first bar is the most green indicating that for those 12 minutes the least number of values fell into the 0-14 range (in this example the count is 1). This ’heat’ information is also supported by the histogram; the most frequently occurring values were those in the 30-40 range, which is the ’hotter’ range in the heatmap.