Ma3696 lecture 4

Looping & Concatenation LECTURE 4

Quick recap of variables For-Next loops Concatenation (&) Loops and Concatenation

SUMMARY

QUICK RECAP

Download Lecture 4 Student Example.xlsm

In Module1, find the procedure called Recap

Declare disposable variables x, y and z as integer.

Assign x a value of 5 Assign y a value of x + z Assign z a value of 10

Output the value of x to cells(1, 1) Output the value of y to cells(2, 1) Output the value of z to cells (3, 1)

EXERCISE. REVIEW OF VARIABLES

Not necessarily in this order

Declare disposable variables x, y and z as integer.

SOLUTIONS. REVIEW OF VARIABLES

Public Sub Recap() Dim x as integer, y as integer, z as integer End Sub

Assign values to each variable.


Public Sub Recap() Dim x as integer, y as integer, z as integer End Sub

x = 5 z = 10 y = x + z

x = 5 y = x + z z = 10

y = x + z x = 5 z = 10

Assign values to each variable.


Public Sub Recap() Dim x as integer, y as integer, z as integer x = 5 z = 10 y = x + z End Sub

Output variable values to cells.


Public Sub Recap() Dim x as integer, y as integer, z as integer x = 5 z = 10 y = x + z End Sub

Cells(1, 1) = x Cells(2, 1) = y Cells(3, 1) = z

x = Cells(1, 1) y = Cells(2, 1) z = Cells(3, 1)

Output variable values to cells.


STEPPING THROUGH CODE

Use the code you typed in the previous exercise

STEPPING THROUGH YOUR CODE

Position screens so you can see both at once


Click a start and end point for stepping through your code (it should turn red).


Click HERE

Click HERE

Run your code (F5) It will pause at the first dot and turn yellow Use shift+F8 to run each line of code


Put your cursor over variables to see their current value. Variables will only show their value AFTER the line

of code as run. If the line is yellow, it means it hasn’t run yet, but it will

run next.

HOVER OVER VARIABLES

Example: Check the value of y

Watch the output to check it is correct Use this technique for checking For-Next loops!

CHECK THE OUTPUT

This code has not run yet

FOR-NEXT LOOPS An Introduction

Enter 1 to 5 into column 1 in Excel

EXAMPLE 1. FOR-NEXT LOOPS

Public Sub ForLoopExample1() Cells(1, 1).Value = 1 Cells(2, 1).Value = 2 Cells(3, 1).Value = 3 Cells(4, 1).Value = 4 Cells(5, 1).Value = 5

End Sub

Very repetitive and inefficient

Use For-Next Loops to improve this code Identify what values are changing Identify what values are staying the same



End Sub

These values are changing

Let i be a counter We have 5 lines of code, so i will count from 1 to 5

Use the counter to change the row & output value


i = 1 i = 2 i = 3 i = 4 i = 5




i = 1 i = 2 i = 3 i = 4 i = 5

When i = 1 row is 1

value is 1

When i = 1 row is i

value is i




i = 1 i = 2 i = 3 i = 4 i = 5

When i = 2 row is 2

value is 2

When i = 2 row is i

value is i




i = 1 i = 2 i = 3 i = 4 i = 5

When i = 3 row is 3

value is 3

When i = 3 row is i

value is i




i = 1 i = 2 i = 3 i = 4 i = 5

For every line of code the row is i

and the value is i

i is an integer I need to declare


i = 1 i = 2 i = 3 i = 4 i = 5

i is an integer I need to declare This is a For-Next Loop


i = 1 i = 2 i = 3 i = 4 i = 5

i is an integer I need to declare This is a For-Next Loop i is the counter – it will increase by 1 each time The first value of i is 1 The last value of i is 5


i = 1 i = 2 i = 3 i = 4 i = 5

i is an integer I need to declare This is a For-Next Loop i is the counter – it will increase by 1 each time The first value of i is 1 The last value of i is 5


i = 1 i = 2 i = 3 i = 4 i = 5

This code will run for each value of i

FOR-NEXT LOOPS

Begin with FOR

End with NEXT

A counter is a letter or word declared as a disposable integer variable

FOR-NEXT LOOPS

Must specify a COUNTER

FOR-NEXT LOOPS

Values the COUNTER will take

Increases by +1 by default END value must be > than START value

Can increment by -1 if necessary to count backwards

FOR-NEXT LOOPS

Must specify START value

Must specify END value

Increases by +1 by default Can increment by -1 if necessary to count backwards

FOR-NEXT LOOPS

The result is the same for both loops

Always START with 1 or 0! You will understand why when you start coding

FOR-NEXT LOOPS

FOR-NEXT LOOPS

CODE to run goes inside the loop

Use Lecture 4 Student Example.xlsm

Write a For-Loop for this: Remember to declare your counter! Loop from 1 to 3 OR from 0 to 2 Write it out the long way first if you need to

EXERCISE 1. WRITE A FOR LOOP

Write this output to these cells

Run your code to ensure it works

Enter 6 to 10 into column 2 in Excel



End Sub





i = 1 i = 2 i = 3 i = 4 i = 5




When i = 1 row is 1

value is 6

When i = 1 row is i

value is i + 5

i = 1 i = 2 i = 3 i = 4 i = 5




When i = 2 row is 2

value is 7

When i = 2 row is i

value is i + 5

i = 1 i = 2 i = 3 i = 4 i = 5




When i = 3 row is 3

value is 8

When i = 3 row is i

value is i + 5

i = 1 i = 2 i = 3 i = 4 i = 5




When i = 4 row is 4

value is 9

When i = 4 row is i

value is i + 5

i = 1 i = 2 i = 3 i = 4 i = 5




i = 1 i = 2 i = 3 i = 4 i = 5

When i = 5 row is 5

value is 10

When i = 5 row is i

value is i + 5




i = 1 i = 2 i = 3 i = 4 i = 5

For every line of code the row is i

and the value is i + 5


Write a For-Loop for this: Remember to declare your counter! Count your loop from 1 to 5 OR from 0 to 4 Write it out the long way first if you need to



(‘E’ is column 5)



Write a For-Loop for this: Remember to declare your counter! Count from 1 to 3 OR 0 to 2 Write it out the long way first if you need to




CONCATENATION &

Join together 2 or more… String variables (i.e., text or words) Text and variable values (integer, double or string) Text and constant values Variable values and constant values Etc…

Use the & to join two or more things together

CONCATENATE MEA N S TO JOIN TOGETHER

EXAMPLES OF CONCATENATION

Not 6!

EXAMPLE 3. CONCATENATION

Public Sub ConcatenateExample3() Dim answer As Double answer = InputBox(“Enter any number”) MsgBox (“You entered ” & answer)

End Sub

Declare a variable called answer



End Sub

Ask the user to enter a number Assign answer the number they enter



End Sub

Ask the user to enter a number Assign answer the number they enter



End Sub

Use a message box to tell the user what number they entered



End Sub

Use a message box to tell the user what number they entered



End Sub

The text in “ ”



End Sub

Use & to join text to a variable value



End Sub

The number entered by the user Variables DO NOT go in “ ”

Find the procedure for Exercise 4. Using 4 input boxes, obtain the following user info: Their name The name of the Uni they attend The course they are studying Their year at Uni (i.e. 1, 2, 3, …)

Display their info in 1 MsgBox using full sentences. e.g. “Your name is…”, “You attend…University”, etc…

Create a button in a worksheet to run this code.

EXERCISE 4. CONCATENATION

Tip: to display part of a message on a new line of a Msgbox, use & vbNewLine & where you want one line to

end and another to begin.

LOOPS WITH CONCATENATION

Enter stock names in row 1 across columns 1-4

EXAMPLE 4. LOOPS WITH CONCATENTATION

Public Sub ForLoopExample4() Cells(1, 1).Value = “Stock1” Cells(1, 2).Value = “Stock2” Cells(1, 3).Value = “Stock3” Cells(1, 4).Value = “Stock4” End Sub



Use the counter to change the col & output value


i = 1 i = 2 i = 3 i = 4




i = 1 i = 2 i = 3 i = 4

When i = 1 column is 1

stock is 1

When i = 1 column is i

stock is i




i = 1 i = 2 i = 3 i = 4


stock is 2


stock is i




i = 1 i = 2 i = 3 i = 4


stock is 3


stock is i




i = 1 i = 2 i = 3 i = 4


stock is 4


stock is i




For every line of code the column is i

and the stock is i

Using Lecture 4 Student Example.xlsm

Write a For-Loop for this: Remember to declare your counter! Count from 1 to 3 OR 0 to 2 Write it out the long way first if you need to


FINAL COMMENTS

When in doubt, write it out!! If you aren’t sure how to write a loop, write it out without

using loops so you can spot the pattern. Then use a loop to make it more efficient.

Step through your code to see what is happening during each loop. Check variable values Check output to cells/ranges

You cannot loop variable names E.g., “mean” & i You have to use arrays (in a couple of weeks) For now, those bits of code will have to be inefficient and long

WHEN YOU’RE STUCK…

You are ready to move on when… LO17: You can name the 4 main parts of a For-Next loop. LO18: Given the output you need, you can write a For-Next

loop to achieve that output. Similarly, given a For-Next loop you can work out what the output/result will be (we will practice this in the lab). This is for one loop, not a nested loop (yet). LO19: You can define the concept of concatenation and

give some examples of how it is used in programming. You can use concatenation to join together values from text, variables and/or numbers. You also know when you need to use “ ” and when you should not use “ ”. LO20: You can combine the use of concatenation with for-

next loops to make code more efficient.

LEARNING OUTCOMES

THE END

Ma3696 lecture 4

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