Please note: This document is a bit old and may need an update. The TwoRavens project has a more recently published user guide on their site: http://2ra.vn/papers/tworavens-guide.pdf.
On the files tab, click on the “Explore” button to initiate TwoRavens Data Exploration and Analysis Tool.
The left panel contains two sets of buttons: (1) Original Data and Subset Data; and (2) Variables, Models, and Summary.
When TwoRavens is initiated, you begin with the original dataset, and thus the Original Data button is selected. You will not be able to select the Subset Data until you have subsetted the data using the subset and select features in the right panel. After you have selected a subset of your data, you may toggle between that subset and the original data. If you wish to select a different subset, you may do so, but note that only one subset is supported at a time.
Each of these tabs displays something different in the left panel when selected. The Variables tab shows a list of all the variables. When a variable name is hovered over, you can see that variable’s summary statistics. The first three variables are selected by default and displayed in the center panel, but you may add or remove variables by clicking on their name in the Variables tab.
The Models tab displays a list of Zelig models that are supported by TwoRavens. A brief model description is visible when hovering on the model name. Depending on the level of measurement of the dependent variable (continuous, ordinal, dichotomous, etc.), particular models may or may not be appropriate.
Note that to estimate a model, you must select one from the list. Currently, please use only Ordinary Least Squares (ls) as we are working on making other models available. (Suggestion: maybe we need to gray out the ones the other ones for the time being)
The Summary tab shows summary statistics when a pebble is hovered over. If one removes the pointer from hovering over a pebble, the previous tab will be displayed. So, if you wish to have the summary tab displayed regardless of where the pointer is, click on Summary before hovering over a pebble. Otherwise, if Variables or Models has been the last tab selected, when the pointer is no longer hovering over a pebble, the table will return to Variables or Models.
The center panel displays a graphical representation of variable relations and denotes variables that have been tagged with certain properties. Variables may be tagged as either a dependent variable, a time series variable, or a cross sectional variable. Each of these are accomplished by clicking on the appropriate button at the top of the screen, and then clicking on a pebble in the center panel. You’ll notice that when a variable is tagged with a property, the fill color becomes white, and the outline (or stroke) of the pebble turns the color of property’s button. Note that to estimate a model, the dependent variable must be selected.
Variable relations are specified by point-click-drag from one pebble to the other. When a path between pebbles has been specified, it is visually presented with a dotted arrow line and may be removed by pushing the delete key on your keyboard.
This section allows you to specify a subset of the data that you wish to estimate the model on, or that you wish to select and see updated summary statistics and distributions, and to set covariate values for the Zelig simulations (this is Zelig’s setx function).
To subset the data, click on the subset button and highlight (or brush) the portion of the distribution that you wish to use. You may remove the selection by clicking anywhere on the plot that is outside of the selected area. Or, if you wish to move the selected region, click inside the selection and move it to the left or right. If no region is selected, then by default the full range of values are used. If more than one variable is selected for subsetting, only the overlapping region is used in the model. If there are no overlapping regions, (i.e., if subsetted there would be no data), then only the first variable is used. Notice that range (or extent) of the selection for each variable is displayed below.
With a region selected, you have two options. First, you may click the Estimate button to estimate a model on using only the specified subset. Second, you may click the Select button. This will not estimate a model, but it will subset the data and return new summary statistics and plots for the subset. You may wish to use this feature to see how a subset will change the Set Covariate (Zelig’s setx) defaults, for example. After selecting a subset, you may toggle back and forth between the subsetted data and the original data by activating the appropriate button in the left panel.
The Set Covariates button plots the distributions of each of the pebbles with an additional axis that contains two sliders, each of which default to the variable’s mean. This is TwoRavens’ equivalent of Zelig’s setx function. Move these sliders to the left or right to set your covariates at the desired value prior to estimation. Notice that the selected values appear below each plot.
After clicking the Estimate button, the model will be estimated and, upon completion, results appear in the Results tab. The results include figures produced by Zelig (and eventually the equation that has been estimated, the R code used to estimate the model, and a results table).
This executes the specified statistical model. Notice the presence of blue highlight on the “Estimate” button while process is running, turning into green upon completion. Note: you cannot use estimate without selecting a dependent variable and a model.
The Force button allows you to control the way layout of the pebbles. To use this feature, first make sure none of the pebbles are highlighted. If one is, simply click on it to remove the highlighting. Second, press and hold the control key. Third, while holding down the control key, click the Force button. Fourth, continue to hold the control key and click on a pebble. You may now release the control key. Click on a pebble and drag it around on your screen.
This is your start over button. Clicking this is equivalent to reloading the Web page or re-initiating TwoRavens.
Scenario Example: