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Creating Plots

After creating a formula, you are ready to create and view some plots. The available plot types are shown on the buttons at the top of the VERDI main window: tile plot, areal interpolation plot, vertical cross section plot, time series plot, time series bar plot, scatter plot, and contour plot. All of these are described in this chapter. Note that not all datasets are appropriate for all plot types.

To generate a plot first highlight a formula in the list of formulas you have created in the Formula pane. You can also see the selected formula in the top right corner of the main VERDI screen (i.e., to the right of the plot buttons). Next, generate a plot by clicking on that plot type’s button. If VERDI needs additional information to generate your chosen plot, a dialog box appears to prompt you for that information.

Each plot contains its own menu bar at the top of its window with options for configuring and exploring that type of plot. The menus may include File, Configure, Controls, Plot, and GIS Layers. The options for each of these menus are described in more detail in Chapter 11 Plot Menu Bar.

Tile Plot

The Tile Plot displays gridded data defined as time steps and layers. It can also display grid cell time aggregate statistics. PDF: ([Fig-@fig:Figure26])) or GitHub:Figure 26 provides an example of the Tile Plot window.

Figure 26. Tile Plot Example

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Time Selection and Animation Controls

At the top left of the Tile plot, the Time Step spin control can be used to change the time step by clicking the up or down arrow. Alternatively, highlight the value shown for the current time step, type in the desired value, and press the Enter key.

Buttons in the top right corner of the plot allow you to use play/stop, reverse, forward, and speed options to control the animation of the plot. Control the speed of the animation through the text box labeled Slow; the default delay is 50 milliseconds between frames. If that text box is not visible, expand the plot window’s width by clicking with the left mouse button on the right edge of the window and dragging to the right. Enter a number in the box for the length of the delay and then press the Enter key. A larger plot with multiple map layers may require a shorter delay between frames than a small zoomed-in plot with few map layers.

Layer Selection

The Layer displayed for the plot can be controlled by clicking on the up or down arrow for the Layer spin control in the top center of the plot.

Grid Cell Time Aggregate Statistics

The pull down menu option labeled Stats provides the option to display grid cell time-aggregate statistics (e.g., per-cell minimum, maximum, mean, geometric mean, median, first quartile, third quartile, variance, standard deviation, coefficient of variance, range, interquartile range, sum, time step of minimum, time step of maximum, maximum 8-hour average, and hours of noncompliance). Although you are still able to use the spinners to change the time step, the values and the chart’s colors do not change.

VERDI calculates the grid cell time aggregate statistics as follows: For each cell (i,j,k) in the currently selected domain (independent of neighboring cells), the aggregated statistical value is calculated over the currently selected time steps. In other words, the aggregated statistical value is calculated for the plotted formula for cells (*i,j,k,*tmin...tmax), with the number of time steps n, where n=(tmax-tmin+1).

• MINIMUM: min (var(i,j,k,tmin), var(i,j,k,tmin+1), ..., var(i,j,k,tmax))

• MAXIMUM: max (var(i,j,k,tmin), var(i,j,k,tmin+1), ..., var(i,j,k,tmax))

• MEAN: SUM / n

• GEOMETRIC_MEAN: ((var(i,j,k,tmin), var(i,j,k,tmin+1), ..., var(i,j,k,tmax)))^(1/n)

• MEDIAN: value at 50^th percentile of (sorted {var(i,j,k,tmin), var(i,j,k,tmin+1), ..., var(i,j,k,tmax)})

• FIRST_QUARTILE: value at 25^th percentile of( sorted (var(i,j,k,tmin), var(i,j,k,tmin+1), ..., var(i,j,k,tmax)))

• THIRD_QUARTILE: value at 75^th percentile of( sorted (var(i,j,k,tmin), var(i,j,k,tmin+1), ..., var(i,j,k,tmax)))

• VARIANCE: ((var(i,j,k,tmin)-MEAN)² + (var(i,j,k,tmin+1)-MEAN)² + ... + (var(i,j,k,tmax)-MEAN)²) / (n - 1)

• STANDARD_DEVIATION: VARIANCE^0.5

• COEFFICIENT_OF_VARIANCE: STANDARD_DEVIATION / |MEAN|

• RANGE: MAXIMUM - MINIMUM

• INTERQUARTILE_RANGE: THIRD_QUARTILE - FIRST_QUARTILE

• SUM: var(i,j,k,tmin) + var(i,j,k,tmin+1) + ... + var(i,j,k,tmax)

• TIMESTEP_OF_MINIMUM: 0-based time step when cell contains its minimum value

• TIMESTEP_OF_MAXIMUM: 0-based time step when cell contains its maximum value

• HOURS_OF_NON_COMPLIANCE: number of time steps that the cell value exceeds a given threshold |{Var(I,j,k,t(i))>threshold}|

• MAXIMUM_8HOUR_MEAN: Ma (M1, M2, ..., Mn-8) where Mi = mean(var(i,j,k,t_(i)), var(i,j,k,t_(i)+1), var(i,j,k,t_(i+2)), ...,var(i,j,k,t_(i+8)), for i = 1..n-8

• count: number of timesteps available in the dataset

• fourth_max: fourth highest value for each grid cell (used to obtain the 4th highest value of your rolling 8 hr maximum CMAQ output file)

• custom_percentile: default is > .12 (use the text box) value at custom ^th percentile of( sorted (var(i,j,k,tmin), var(i,j,k,tmin+1), ..., var(i,j,k,tmax)))

• layer_sum: Sum values at all layers (by default) or at layers within the user selected layer range set by "Use Layer Range" for each grid cell at each time step

• layer_mean: layer_sum/number of layers

Specify Layer Range when use 'layer_sum' and 'layer_mean' from the above aggregated Statistics dropdown menu in a tile plot

User should check the checkbox of 'use layer range' and specify the layer range before clicking on the 'Tile Plot' button on the top menu for the specified layer range to take effect.

Areal Interpolation Plot

The areal interpolation plot displays the interpolated value of the selected formula for each polygon in the selected area file. Compare the colors of the polygons to those shown in the legend, to see the relative values of the formula for each polygon area. The Areal Interpolation Plot includes several capabilities that are not available for other plot types, so these are described below.

Options Menu

The Areal Interpolation Plot menu contains an Options menu to allow the user to change the map to display either the Area Averages PDF:([Fig-@fig:Figure27])) or GitHub:(Figure 27), the Area Totals PDF:([Fig-@fig:Figure28])) GitHub:(Figure 28), or the value of the formula contained in the Gridded Dataset (uninterpolated) PDF:([Fig-@fig:Figure29])) GitHub:(Figure 29). The Options pull-down menu may also be used to display All area segments that are loaded in the area list, or to display only the area segments that are selected by highlighting the name field from the area list PDF:([Fig-@fig:Figure30])) or GitHub:(Figure 30).

Figure 27. Areal Interpolation Plot: Area Average

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Figure 28. Areal Interpolation Plot: Area Totals

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Figure 29. Areal Interpolation Plot: Show Gridded Data

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Figure 30. Areal Interpolation Plot: Show Selected Areas

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Areal Values for Polygon Segment

To view the area, total value, and average value for a selected polygon segment use the mouse cursor to hover over a polygon on the map. The values are shown at the bottom left of the information panel PDF:([Fig-@fig:Figure31])) or GitHub:(Figure 31).

Figure 31. Areal Values for a Selected Polygon

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View and Export Areal Interpolation Plot Data in Text Format

To view the average and total interpolation values for selected formulas in a spreadsheet format, right click on the Areal Interpolation Plot and select Area Information PDF:([Fig-@fig:Figure32])) or GitHub:(Figure 32), then click on the radio button next to All, to select all area regions, click on the Formula Name, then click on OK. The Area Information Spreadsheet contains four columns: the identification number from the name field for the polygon, the total area, average interpolated value, and total interpolated value PDF: ([Fig-@fig:Figure33])) or GitHub:(Figure 33). At the top of the Area Information tab, the user may select File>Export to export the data to a spreadsheet file (Figure 34). The save popup window allows the user to specify with either a text (.txt) or comma-separated-values (*.csv) format, also known as a comma-delimited text file (Figure 35).

Figure 32. Right Click on Area Plot

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Figure 33. Area Information in Columns

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Figure 34. Export to a Text File

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Figure 35. Name and Save the Text File

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Export Areal Interpolation Plot Data to Shapefiles

At the top of the Area Information tab PDF:([Fig-@fig:Figure36])) or GitHub:(Figure 36), the user may select File>Export Shapefiles to export the data to a shapefile. In the Save popup window PDF:([Fig-@fig:Figure37])) or GitHub:(Figure 37), input the name in the File Name field, and select file type: Shapefile (*.shp). The data provided in the Area Information report (i.e., name, total area, average value, total value) are exported to the shapefile. A GIS program such as User-friendly Desktop Internet GIS (uDig; http://udig.refractions.net/), an open-source Java program, or QGIS (http://qgis.org/en/site/) may be used to view the shapefiles generated by VERDI. The shapefiles are saved as five separate files that must be kept together as part of the ESRI format (*.shp, *.dbf, *.prj, *.shx, and *.fix). There are no units assigned to the data that are saved in the shapefile, so it is important for the user to keep a copy of the comma-delimited text file, or to keep some alternative text file that specifies the units for each data field.

Figure 36. Export Shapefile

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Figure 37. Name and Save Shapefile

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Vertical Cross Section Plot

The vertical cross section plot allows you to show a slice of data PDF:([Fig-@fig:Figure38])) or GitHub:(Figure 38). A popup dialog box PDF:([Fig-@fig:Figure39])) or GitHub:(Figure 39) prompts you for information needed to create the plot. Enter either the column to be used (for an x-axis cross section) or the row to be used (for a y-axis cross section) in the plot. The current time step on the plot can be changed using the Time Step spinner control above the plot, which also changes the date and time shown in the bottom of the plot. There is also a Column spinner control to change the column number (or row number). The cross-section column number (or row number) is included in the title of the plot and changes as you change the spinner control.

Figure 38. Vertical Cross Section Plot

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Figure 39. Vertical Cross Section Dialog Box

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Time Series Plot

The time series plot shows a line graph with the average values over time (Figure 40). The plot is made for the formula’s selected domain, layer range, and time-step range. Each time step’s data are averaged linearly to produce that time step’s data point. The current layer can be changed using the Layer spinner control above the plot. The layer value listed in the title is updated when you change the layer.

Figure 40. Time Series Plot

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Time Series Bar Plot

The time series bar plot shows average values over time in a bar plot format (Figure 41) rather than a line format (Figure 40). Other than that, the description of this plot type is the same as for the time series line plot (see Section 10.4).

Figure 41. Time Series Bar Plot

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Scatter Plot

The scatter plot shows the relationship between two formulas using dots PDF:([Fig-@fig:Figure42])) or GitHub:(Figure 42). Specify the formulas using the dialog box that comes up before the plot is displayed (Figure 43). The current time step and layer can be adjusted using the spinner controls above the plot. The data from a scatter plot may be exported by selecting the File menu option and then selecting Export data. If your dataset has more than one layer or time step, a popup window (see PDF:GitHub:Figure 44) allows you to specify whether you want to export the data for the current layer, or for all layers, and for the current time step, or for all time steps. Specify the time and layer ranges, and then click the OK button. A Save popup dialog box appears. Navigate to the directory in which you want to save this file and enter a file name with a .csv extension. The CSV file will be comma-delimited, and will contain the following columns of data: layer, time step, x-axis formula, y-axis formula. You can open this file in a spreadsheet program if your data does not contain too many rows (e.g., 65,536 or 1,048,576 depending upon version of Microsoft Excel).

Figure 42. Scatter Plot

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Figure 43. Scatter Plot Dialog Box

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Figure 44. Scatter Plot Export Data into a CSV file

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Contour Plot

The contour plot shows a three-dimensional (3-D) representation of values for a gridded dataset (e.g., one that can be used in the Tile Plot) PDF:([Fig-@fig:Figure45])) or GitHub:(Figure 45). Note that the 3-D contour plot is displayed in its own window (i.e., not in the VERDI window). The current time step and layer can be adjusted using controls above the plot. You can also animate the plot over time using an option in the Plot pull-down menu PDF:([Fig-@fig:Figure46])) or GitHub:(Figure 46). In addition, the contour plots can be rotated in three dimensions to achieve different viewing angles by using the left mouse button to grab and rotate the plot PDF:([Fig-@fig:Figure45])) or GitHub:(Figure 45).

Figure 45. Contour Plot

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Figure 46. Contour Plot Menu Options

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Figure 47. Rotated Contour Plot

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