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Locus

Another exclusive Foundation RISCWorld application

Dialogue boxes

Functions dialogue box

Locus permits the use of function notation for formula input and the letters 'f' to 'o' are recognised by the internal formula translation routines as function names. It is important to remember this because it means you must not use these reserved letters as constants.

Once a function has been defined it is saved to a file inside Locus where it will remain until the contents of this dialogue box changes.

As an illustration, in the example shown the function definition f(x) is defined as 'sinx + cosx'. This means that the formula y=f(x) will draw the graph of y=sinx + cosx.

This capability is useful as typing f(2x) will draw the graph of y=sin2x +cos 2x and typing 2f(x) will produce the graph y=2(sinx + cosx). It is particularly valuable when teaching function transformations and in looking at families of related functions. (see the next section.)

Clicking on the OK button will reset the preset functions to their new values and clicking on the Cancel button closes the window without altering anything.

Families dialogue box

The icon at the top of the Graph Families dialogue box shows the number of graphs to be plotted and the remaining writable icons allow you to set the required increments for each of the constants.

If any of these icons are left blank those constants will remain the same throughout the operation.

When everything is set to your satisfaction click on the <OK> button to accept the values or press <Cancel> to reject them.

When the graphs have been plotted the constants will revert to their original values.

Constants dialogue box

This lets you preset constants. When you receive Locus you should find that 'p' is set to the value of pi (3.14......) and 'e' is set to the value of e (2.718.....). The letters f-o are missing as these are recognised by Locus as user defined functions. t, x & y are also missing as they are defined as variables.

You can alter any of the values or add new ones as you wish and then set them by clicking on the OK button or you can save your values as the default set by clicking on the Save button. Cancel closes the window and changes nothing.

Print dialogue box

This displays information about the printer and the various settings that will enable the user to print the graph at the right point on the paper and at the correct size.

• Printer shows the name of the currently active printer.
  
• Resolution shows the current print resolution of your printer.
  
• Copies sets the number of copies of the graph that will be printed.
  
• Cancel closes the Print window.
  
• Print begins printing.

Pressing Escape at any time during the printing will abort printing and return control to the desktop.

This dialogue box can be accessed via the Print Hot Key.

Formulae dialogue box

This lets you alter the formulae which appear when you click on the formula menu icon on the main window pane. You can have up to 50 preset formulae in these menus although if the menus become too large it becomes difficult to find the entry required.

There are five files, one for each of the five formula based modes of operation: cartesian, polar, implicit etc. and the appropriate data is shown in this window for the mode you are in at the time.

After changing the formulae clicking the OK button resaves the formula file.

If you delete formulae from the menu you need not worry about leaving empty icons, Locus will deal with these automatically.

This dialogue box can be accessed via the Hot Key ^E.

Coordinates Dialogue Box

This allows you to enter small data sets without recourse to CSV, SID or Text files.

The topmost writable icon takes the titles for the horizontal and vertical axes. These must be separated by a comma as this window is read by the same function that deals with other input data sets.

The rest of the writable fields can contain the coordinates of the points you want to plot. The plotting style of the points is controlled by the 'Effects' dialogue box.

The Clear button empties all fields in the window.

As well as entering data manually can drag small data set files to the arrow icon in this window to load them.

Internal filer window

This window allows you to save dataset files into your own personal directory and from there they can be deleted, loaded into a text editor or loaded into Locus. You can also create new data files yourself from this window. This allows you, the user to manipulate datafiles within Locus without having to move the main window aside so that you can drag a data file from a filer window onto the application window.

When you received your copy of Locus, you should have also received a copy of a tiny application directory called !LocusData. You should make copies of this for everyone who is going to use the application.

Suppose that Locus is on a network and a class of students is using the internal filer simultaneously. Everyone is accessing the same copy of Locus from the server but this way they can all use different sets of files because the LocusData folder is kept in their personal network space.

In order to use the internal filer, you should double click on your LocusData application window. This will open the directory where your files are stored and tell Locus where to look for files.

• Cancel will close the window without doing anything at all.
  
• Open File will open any file that the user has selected in the pane window. If nothing happens when you click on this button, load your text editor and it will work.
  
• Delete File will any delete any file(s) that the user has selected in the pane window.
  
• Clicking on Delete All will empty Locus of all saved datafiles.
  
• Clicking on Save file will open a save box which the user can use to drag the selected file to a directory of their choice.
  
• Clicking on Load file will load the selected file(s) into Locus.

To load a set of data files into Locus in this way you drag the files onto the 'arrow' icon.

Clicking on New file will open a text window in whatever text editor you have loaded. You can then save the edited file back into Locus. If no text editor is loaded then nothing will happen.

Clicking on the Reset button will update the pane window directory.

Title Dialogue Box

This lets you write up to 256 characters onto the screen in any font, fontsize and desktop colour.

Fill in the fields and click on the OK button to display the text. By default the text will be printed at the top left hand corner of the screen but you can move it by clicking on it to select it and then dragging it around the screen. Clicking anywhere outside of the box will deselect it.

This dialogue box can be accessed via the Hot Key ^T.

Transformations dialogue box

This enables the user to transform data sets in a variety of different ways. Once a data set has been loaded by dragging the file icon onto the Locus window the Transform entry in the main menu becomes selectable and clicking SELECT on it will open the Transformations window.

There are four main transformations that can be applied to a data set:

• Rotation
  
• Enlargement
  
• Reflection
  
• Translation

First click with SELECT on the transformation you require and then fill in the appropriate fields.

Clicking on the Apply button will apply the transformation to the data set. The transformation will be applied to the last data set loaded so clicking on Apply a second time will transform the previously transformed set.

This dialogue box can be accessed via the Hot Key F4.

Matrix Dialogue Box

The window performs similar operations to the transform window but the input can be made as a 2x2 matrix.

You can use trigonometric functions and constants in the matrix fields but you must put the constant values in brackets. For example, if you type 'cos(p/2)' in one of the fields, the brackets are essential as 'cos p/2' produces the effect '(cosp)/2' which, if part of a rotation matrix, would produce a transformation of Rotation of pi radians followed by an enlargement scale factor 0.5 (all centre (0,0)).

This dialogue box can be accessed via the Hot Key F5.

Statistics Info and Dialogue Box

This main purpose of this window is to display information about your data set, transformed or otherwise.

It gives all of the information required, and in addition can calculate the correlation coefficient and the least squares regression line.

If you want to draw the Least squares regression line onto the data set graph click on the Transfer Equation button to transfer the formula to the formula input icon on the main window and then click on the Plot button as usual.

This dialogue box can be accessed via the Hot Key F6.

Settings Dialogue Box

This window contains seven option icons which enable you to set up your graphs according to preference.

1. Show Assymptotes
   When set this makes Locus draw assymptotes (a dotted vertical line) at the borders of any area of the graph where the function is not defined. For example the graph of y=1/(x+2) will have an assymptote at x=-2. When it is off Locus will not draw them.
   
2. Show Plot
   Locus plots graphs in a variety of different ways to give the user the maximum choice. Most graph plotters do not permit the user to see the graph while it is being plotted but Locus does allow you to do this if Show Plot is on. Plotting will be slower, but this feature can be very useful.
   
3. Show Axes
   If Show Axes is off, the axes will disappear. Normally you would want to see them but it may be useful not to have them at certain times.
   
4. Show Grid
   If Show Grid is on the graph will be covered with a lattice. This can be turned on and off at any time, whether graphs have been drawn or not, although it is best to decide at the start whether you want this on or off as redrawing can take a while if the plot is complicated.
   
5. Show Minor Axis Divisions
   If this is set the axes will show small marks between the slightly larger, labelled, marks. Minor divisions are not labelled. The number of divisions will alter automatically dependent upon the size of the range settings.
   
6. Show Axis Markers
   If this is set numbers will be displayed at intervals along the horizontal and vertical axes to show the scale.
   
7. Show Axis Labels
   If this is set the axis labels will be displayed. By default these are 'x' and 'y'.

This dialogue box can be accessed via the Hot Key F7.

Effects Dialogue Box

From here you can set the options which control the appearance of the graph such as fonts, colours and data marks.

• Fonts sets the font and font size for the axis markers.
  
• Colours sets the various colours used.
  
• Mark sets the shape used to denote a point in a data set. The choice is -
  
  • Dot
    
  • Cross (square)
    
  • Cross (diagonal)
    
  • Square (small, empty)
    
  • Square (large, empty)
    
  • Diamond (small, empty)
    
  • Diamond (large, empty)
    
  • Square (small, filled)
    
  • Square (large, filled)
    
  • Diamond (small, filled)
    
  • Diamond (large, filled)

The 'Connect marks' option button sets whether the marks in a data set will be joined to each other in the order of input.

This dialogue box can be accessed via the Hot Key F2.

Foundation RISCWorld