ScatterBrain™ for Javascript

 

 

Instructions for using the Javascript version of ScatterBrain, used on this web page, appear below. The name “ScatterBrain” has been used with several versions of this software. The Java version is described at www.polinetworks.com/SB (case sensitive).

 

The data on this web page—www.polinetworks.com/big78  --includes several data elements for each of the 3,195 elementary and middle schools associated with Texas’ largest 78 school districts. In addition to STAAR1 test passage rates and several demographic variables, the per pupil General Fund Operations Expenditures are also included for each school.  The expenditure data are for the school year 2016-2017. STAAR1 refers to the state accountability tests, evaluated on the “approaching grade level” criterion, which is the least demanding.  The STAAR1 and demographic data are from the 2015-2016 school year. The percentage passing rates used herein refer to the percentage of the tested students at each school who passed all tests—reading, mathematics, and writing (in certain grade levels).

 

The essence of a scatter plot type diagram is that it visually depicts a relationship between two variables. Even when a pronounced relationship is apparent, there will still likely be many points that don’t fall “on the line”.  Often these outliers are of special interest.  The code used on this web page permits interactively identifying the points displayed, including such outliers.  This can be done with the aid of the mouse, drawing a rectangle around one or more points, or by name lookup, using a name select list.

 

Another feature is the ability to highlight all of the elementary and middle schools associated with a selected school district.  In addition, certain calculations can be immediately performed on subsets of points, with the results—totals, simple averages, or weighted averages—shown for multiple subgroups, which can then be  displayed and compared with each other.

 

In the graph shown, the STAAR1 pass rates are on the vertical axis, and the percentage of students who are classified as economically disadvantaged in each school are plotted on the horizontal axis. Students are so classified if their family income is low enough that they qualified for the Federal free or reduced-price lunch program during the prior school year.

 

The reason for restricting the data to the largest 78 school districts was to ensure sufficient numbers of elementary and middle schools to enable a statistical comparison of the average levels of spending between the high-poverty and low-poverty groupings of schools within each district. These comparisons can be duplicated using the interactive features of the software used on this web page, which are described in the following Instructions for Using ScatterBrain(js).

 

Larry Toenjes

ltoenjes@aol.com

Instructions for using ScatterBrain (js) at www.polinetworks.com/big78

 

  1. To identify a single point with the mouse, do the following:

(a)   Using the mouse, place cursor near a point or points of interest;

(b)   Click the left mouse button. (“Click” it, i.e., don’t hold the LMB down and “drag” it.)

(c)    Move the mouse/cursor until the resulting red rectangle encloses a point or points of interest;

(d)   Click the left mouse button again.  One of the points inside the rectangle should begin blinking on and off.

(e)   If there was more than one point enclosed in the rectangle, clicking the LMB once again will advance to the next point found in the rectangle and it will then begin blinking;

(f)    Continue until the last point is blinking. Clicking the LMB once more will cause the last point to stop blinking. The process may be repeated.

(g)   Note that as each school is identified certain data elements are written to the data window beneath the graph.

  1. This web page has been tailored so that individual schools can only be identified with a drop-down selection list after first selecting a school district.  Instead of “selecting” the schools in a district, they can alternatively be highlighted. To highlight all of the schools in a district, proceed as follows:

(a)   First click the LMB with the cursor on the [Reset] and [Clear] buttons.

(b)   If it is only desired to highlight—as opposed to selecting-- the schools in a district, the Highlight/Select button [Hlt/Sel] should not be colored red. If the button is already red, click on it and it will change to white, indicating the Highlight mode.

(c)   Click on the select list box, which will initially be displaying the text “ALL DISTRICTS”.

(d)   From the resulting list of names for the 78 large districts, select the one desired by clicking the mouse (LMB) on its name. The schools in the selected distritd will be highlighted with colored circles.

(e)   The schools in additional districts can be highlighted by repeating steps (c) and (d).

(f)    Note that as each district is selected, aggregated data are written beneath the graph.  In the case of ENR, the aggregate is of course the sum of the enrollments of the elementary and middle schools in the selected district.  For the remainder, the figures are weighted averages for all of the schools, in each district, with enrollments used to weight the values for each school.

  1. If instead of merely highlighting the schools in a district it is desired to discard from the graph all of the schools not in a given district, proceed as follows:

(a)   After clicking on the [Reset] and [Clear] buttons, click on the [Hlt/Sel] button, changing it to color red.

(b)   Select a school district’s name from the district drop-down select list. Only the schools in the selected district will be left in the diagram.

(c)   The remaining schools can be further sub-selected by clicking on either the elementary school button [Elem] or the middle school button [Mid]. Clicking on the [All] button removes these sub-selection options

 

  1. After selecting schools by selecting a particular school district, it is possible to identify an individual point/school using the school select list, just to the right of the one that was used to select districts:

(a)   Place the cursor in the select box window (the first school name in the list appears there) and click the LMB;

(b)   Scroll to the name of the school of interest and click (LMB) on the name.

(c)   The corresponding point in the graph should begin blinking and data pertaining to the selected school displayed in the data window beneath the graph.

(d)   Additional names can be selected and identified by repeating (b).

(e)   Note that elementary schools appear in alphabetical order at the top of the list, followed by the middle schools.

 

  1. Whenever a point is blinking after using, either method 1 or method 4 above, the name can be deposited on the graph to make it easier to relate the points on the graph with the data shown for those already identified.  This is done as follows:

 

(a)   Whenever a point is blinking use the mouse to position the cursor at the location in the graph where it is desired for the name to be displayed.

(b)   With the cursor positioned, press the Ctrl key.

 

  1. Clicking on the [Mid] button highlights in blue all of the middle schools.  Clicking on the [Elem] button highlights all of the elementary schools in aqua.  Clicking on the [All] highlights all points.                                                                                               
  2. Clicking on the [Clear] button at any time restores the graph and the data window to the initial condition.        Clicking on the [Reset] button re-selects all of the schools in all districts.                                                                                                 
  3. Regression line:  Clicking on the button labeled [Regress] causes the line of best fit to be drawn through the points in the graph.  In fact, this is the default situation. Called the regression line or least squares line, this line indicates the average linear relationship, if any, between the two variables represented by the scatter plot.  Clicking on the [Regress] button causes the line to appear or disappear.                                                                                                                               

9.      Multi-point functions:  Clicking on the [Multi] button turns it red, indicating the program is in the mode that operates on multiple points at once, even on all of them.  With the [Multi] function on (red) draw a box around numerous points. (Remember click once, move the mouse, click again.)  When the LMB is clicked the second time, completing the box, certain calculations will be performed on the row values in each column.  Depending on instructions in a “setup file” that the program reads along with the data, the calculation on each column is one of the following three:  (a) total; (b) simple (arithmetic) average; (c) a weighted average. With school-related data the most common weighted average is one which weights by the number of students in the school, school district, or charter system. Clicking on the [Notes] button will display information indicating which function is applied to each column in the data table.       

10.  Percentage calculation and display:

(a)   When a rectangle is being formed when in the Multi-mode (see step 9), as the size of the rectangle is being changed, before clicking the second time, the percentage enrolments of all students in all schools is calculated.  As you change the size of the rectangle, thereby including more or fewer schools, this percentage is constantly re-calculated.  These percentage figures, as well as the numbers of students on which they are based, appear in the page tab of this web page, at or near the top of the screen.  The numbers will replace the page identifier—polinetworks.com/big78. This feature is useful if it is desired to compare the characteristics of two different sets of schools with approximately the same numbers of students in each set.  This feature is active if the [PctOn] button is selected (red).

(b)   If only the schools in a single district are being displayed, as in item 3 above, then the percentages displayed refer to just the enrollment total of the schools in the selected district,                        

(c)   If either elementary schools or middle schools have been selected, by selecting/highlighting the [Elem] or [Mid] buttons, then the percentage figures seen in the page tab will refer only to the elementary or middle school subset.  The student count that appears in the page tab, however, is not affected by either the elementary or middle school subsets.

(d)   Be aware that an older, slower micro processor might not be able to handle these instantaneous percentage calculations acceptably.  If that occurs, or this feature does not work properly with a particular browser or tablet computer, the feature may be turned off by de-selecting the [PctOn] button.

(e)   Note of caution:  Because of extremely small timing difference and possible minute movements of the mouse cursor when the LMB is depressed, thus completing the selection rectangle, it can happen that the number of students shown in the page tab, following the percentage figure, my differ from that shown in the data window itself.  If that occurs, the percentage calculation would not correspond to the student count shown in the data window. If this should happen, the rectangle should be re-drawn, and care taken that the mouse does not move when the LMB is depressed. Should be a recurring problem, the equivalent of the LMB adjacent to a laptop computer’s touch pad could be depressed instead of depressing the one on the mouse itself, assuming a laptop computer is being used.                                                                                    

                                                                                                     

11.  The [Ctrl] button: If using a tablet computer touching the [Ctrl] button while one of the dots is blinking will result in the name being written next to the dot.  Without a mouse, and a keyboard with a Ctrl key, names cannot be positioned precisely on a tablet (as was described in (5) above when using a computer).                                                                                                                              

                                                                                                     

12.  Reset button:  If a district has been “selected” as in (3) above and it is desired to return the presentation showing all schools in all districts, click on the [Reset] button.  One other use of the [Reset] button is as follows:  if a large number of points have been included in a rectangle and it is not desired to keep clicking the mouse and identifying all of them, clicking on the [Reset] button will jump out of the loop.                                                                                                                          

13.  Browsers:  This Javascript version of ScatterBrain works well with Chrome and recent versions of Explorer.  Using it with Firefox, however, was not satisfactory, as the creation of the capturing rectangles left red smears on the screen.  This could, of course, change. Android-based tablets permit a mouse to be plugged in, which can be used to create the rectangles used in identifying points or performing multi-point calculations. Names can also be precisely positioned on an Android-based tablet screen by positioning the cursor at the desired location with a mouse and touching the [Ctrl] button to write the name. Remember, names can only be written to the screen while the dot for a particular district is actually blinking.  This can occur either by using the mouse method of enclosing points in a rectangle, or by using the name selection list, as described previously.                                                                                      

14.  Finally, if a touch-screen tablet is being used, without a mouse, mouse-clicks are simulated by touches.  Therefore, districts can be selected by touching the screen two times, in effect determining the positions of the opposite corners of a rectangle.  Repeated touching of the screen will result in stepping through all of the points highlighted by this resulting rectangle.  If the [Multi] function is “on” (red), the aggregate calculations will be carried out for all of the schools contained in the implicit rectangle defined by the two points on the screen which were touched.