Dialog Boxes Applications of Cell-Arrays Reminder of Symbols Dialog Boxes listdlg() msgbox() questdlg() menu()

1. Reminders on Symbols Creating/hard-coding: Braces { } Referencing to content: Braces { } Augmenting: Brackets [ ] Referencing to container: Parentheses () Most likely to be used!

2. Dialog Boxes 3

2. Dialog Boxes Dialog boxes are “popup windows” that allows us another means to communicate with the user. Some dialog boxes to collect input: inputdlg(), listdlg(), menu(), questdlg() And some to produce output: msgbox(), warndlg() 99% of the time, the command deals with cell arrays, either as arguments, as return values, or both! 4

3. listdlg() listdlg() – Create and open list-selection dialog box Major Advantage: User does not have to type anything Fewer spelling errors!

>>doc listdlg() <enter> This function gives 2 return values

[Selection,ok] = listdlg('ListString',S) Selection is a vector of indices of the selected strings (in single selection mode, its length is 1). Selection is [] when ok is 0. ok is 1 if you click the OK button, or 0 if you click the Cancel button or close the dialog box. Double-clicking on an item or pressing Return when multiple items are selected has the same effect as clicking the OK button. The dialog box has a Select all button (when in multiple selection mode) that enables you to select all list items.

listdlg() return values What will the first return value be after this executes? {'Primary Booster','Secondary Boosters'} [1 3] {1, 3} None of these

listdlg() return-values What will the first return value be after this executes? ['Primary Booster','Secondary Boosters'] [1 3] {1, 3} None of the above Remember: you choose the name of variables used to collect the return values.

[Selection,ok] = listdlg('ListString',S) Selection is a vector of indices of the selected strings (in single selection mode, its length is 1). Selection is [] when ok is 0. ok is 1 if you click the OK button, or 0 if you click the Cancel button or close the dialog box. Double-clicking on an item or pressing Return when multiple items are selected has the same effect as clicking the OK button. The dialog box has a Select all button (when in multiple selection mode) that enables you to select all list items.

[Selection,ok] = listdlg('ListString',S) Selection is a vector of indices of the selected strings (in single selection mode, its length is 1). Selection is [] when ok is 0. ok is 1 if you click the OK button, or 0 if you click the Cancel button or close the dialog box. Double-clicking on an item or pressing Return when multiple items are selected has the same effect as clicking the OK button. The dialog box has a Select all button (when in multiple selection mode) that enables you to select all list items. If user hits cancel or closes the dialog box, an empty vector is returned, AND ok is set equal to 0. This means the second return value can be used to see what the user did!

What did user do? Did user hit ok? Did user hit cancel? Either way: Had s/he selected anything anyway?

What did user do? Did user hit ok? Did user hit cancel? Either way: Had s/he selected anything anyway? If user did click ok, then ok will be true, which equals 1. If user did not click ok, then ok will be false, which equals 0.

[Selection,ok] = listdlg('ListString',S) Inputs are in parameter/value pairs (i.e. they go 2 by 2): Parameter goes 1st, value of the parameter goes 2nd. The actual string:

Experiment in the command window!

Experiment in the command window! myList is a CELL ARRAY of strings: { } Why cell arrays? The length of each selection varies widely, and an regular array would not be rectangular.

Experiment in the command window! What button did the user hit? The 'ok' button The 'cancel' button The [x] that closes the window Either b or c None of the above

A second parameter Though additional arguments are not necessary, you may choose to add them AS A PAIR. For example:

2nd PAIR of inputs. The Select All button is gone.

2nd PAIR of inputs. What did the user select? It cannot be determined __________________________

3.a. Full Example Create a program that estimates the time an aircraft takes to travel a certain distance. Aircrafts possible, with their average speeds are: Cessna 150, 198 kph Boeing 787, 950 kph Concorde, 2147 kph Cessna 421, 444 kph

Algorithm %prompt user for type of airplane (error?) %prompt user for distance to travel (error?) %calculate/display Presented is the evolution from: Option1: use input() and if. (week 2,3.4) Option2: use input() and vectors. (week 10) Option3: using listdlg(), vectors and cell-arrays.

#1. input(), if and while %prompt user for type of airplane type = input('Enter the type of airplane: \n1 – cessna 150\n 2-Boeing 787\n3-Concorde\n4-Cessna 421\n Enter now: '); %prompt user for distance to travel distance = input('Enter the distance (km): '); %calculate/display if type == 1 %cessna 150 travelTime = distance/198; fprintf('With this plane, it will take %.2fhrs.\n', travelTime); elseif…. Add while loops to trap errors.

#2. input(), vectors, while %prompt user for type of airplane type = input('Enter the type of airplane: \n1 – cessna 150\n 2-Boeing 787\n3-Concorde\n4-Cessna 421\n Enter now: '); %prompt user for distance to travel distance = input('Enter the distance (km): '); %data base of speeds speeds = [198, 950, 2147, 444]; %calculate/display travelTime = distance/speeds(type); fprintf('With this plane, it will take %.2fhrs.\n', travelTime); Add while loops to trap errors. Reference the correct value in the vector, using the index.

#3. listdlg(), arrays, while %prompt user for type of airplane myPlanes = {'Cessna 150', 'Boeing 787', 'Concorde', 'Cessna 421'}; type = listdlg('ListString', myPlanes,'selectionmode', 'single'); %prompt user for distance to travel distance = inputdlg('Enter the distance (km): '); %data base of speeds speeds = [198, 950, 2147, 444]; %calculate/display travelTime = distance/speeds(type); fprintf('With this plane, it will take %.2fhrs.\n', travelTime); Add while loop to trap errors, and convert to number Reference the correct value in the vector, using the index.

#3. Output

#3. Output Note: For usability, once a program starts with dialog boxes, it should continue with dialog boxes… >> not in the command window..

4. msgbox() A little improvement: %calculate/display travelTime = distance/speeds(type); resultString = sprintf('With this plane, it will take %.2fhrs.\n', travelTime); msgbox(resultString)

4. msgbox() A little improvement: %calculate/display travelTime = distance/speeds(type); resultString = sprintf('With a %s, it will take %.2fhrs.\n', ??????, travelTime); msgbox(resultString) Task: Replace "this plane" by the actual name!

4. msgbox() %prompt user for type of airplane myPlanes = {'Cessna 150', 'Boeing 787', 'Concorde', 'Cessna 421'}; type = listdlg('ListString', myPlanes,'selectionmode', 'single'); Remember: this is the index (i.e. location) of the string selected. This is the cell array of all the names. To reference the name selected using the index selected: planeSelected = myPlanes{type}; REFERENCE the CONTENT, using curly braces.

4. msgbox() A little improvement: %calculate/display travelTime = distance/speeds(type); resultString = sprintf('With a %s, it will take %.2fhrs.\n', myPlanes{type}, travelTime); msgbox(resultString)

Make the program error proof! %prompt user for type of airplane myPlanes = {'Cessna 150', 'Boeing 787', 'Concorde', 'Cessna 421'}; [type ok] = listdlg('ListString', myPlanes,'selectionmode', 'single'); %if user hits ok, continue if ok==1 %prompt user for distance to travel distance = inputdlg('Enter the distance (km): '); %code as before else %user hit cancel of closed box.. %do other stuff end

Done with that example. Note how much our programs have improved since week 2, and yet not too many lines of code were required. Hopefully, you're pausing and coding this at home. Use the tools in the final project if you want. Make sure to error-proof accordingly.

5. questdlg() Typical call: button = questdlg('qstring','title','str1','str2', 'str3','default') qstring = Question to ask the user title = Title for dialog box str1 = String to show on Button #1 str2 = String to show on Button #2 str3 = String to show on Button #3 default = String that is the default button button = string on the button that was clicked Caution: Maximum of 3 buttons.

5. Quick experiment button = string on the button that was clicked

6. menu() – vertical menu Typical call: button = menu('qstring','bt1','bt2',……,'btn') qstring = question to ask user bt1 = String to show on Button #1 bt2 = String to show on Button #2 Can have as many options as desired. There is no default answer. Return value: Button number clicked (not the string)

6. menu(), with cell arrays

6. Output

What's next??? Yes, we are done with cell arrays and dialog boxes.. So what's next?

Wrapping Up Dialog boxes are user friendly but require a little more coding If you’re writing a “quick and dirty” program, dialogs may be overkill – consider the command window instead. We saw: inputdlg() listdlg() msgbox() questdlg() menu() It’s difficult to memorize syntax. Practice it and use MATLAB Help to remind yourself quickly!