1 / 20

Chapter 7 – Arrays

Chapter 7 – Arrays. 7.1 Creating and Accessing Arrays 7.2 Using LINQ with Arrays 7.3 Arrays of Structures 7.4 Two-Dimensional Arrays 7.5 A Case Study: Analyze a Loan. 7.4 Two-Dimensional Arrays. Declaring a Two-Dimensional Array Variable Implicit Array Sizing and Initialization

lundy
Télécharger la présentation

Chapter 7 – Arrays

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 7 – Arrays 7.1 Creating and Accessing Arrays 7.2 Using LINQ with Arrays 7.3 Arrays of Structures 7.4 Two-Dimensional Arrays 7.5 A Case Study: Analyze a Loan

  2. 7.4 Two-Dimensional Arrays • Declaring a Two-Dimensional Array Variable • Implicit Array Sizing and Initialization • The ReDim Statement • Filling a Two-Dimensional Array with a Text File • Outputting an Array

  3. Declaring a Two-Dimensional Array Variable • Two-dimensional arrays store a table of items of the same type. • Consider the rows of the table as numbered 0, 1, 2, … m and the columns numbered 0, 1, 2, … n. • The array is declared with DimarrayName(m, n) AsDataType • The item in ith row, jth column is denoted arrayName(i,j)

  4. Declaring a Two-Dimensional Arrays An unsized two-dimensional array can be declared with a statement of the form DimarrayName(,) As varType

  5. ReDim and Two-Dimensional Arrays • An already-created array can be resized with ReDimarrayName(r, c) • which loses the current contents. • When Preserve is used … ReDim PreservearrayName(r, c) • Only the columns can be resized. • ReDim cannot change the number of rows in the array.

  6. Implicit Array Sizing and Initialization Arrays can be initialized when they are declared. DimarrayName(,) As DataType= {{ROW0},{ROW1}, {ROW2}, ..., {ROWN}} declares a two-dimensional array where ROW0 consists of the entries in the top row of the corresponding table delimited by commas, and so on.

  7. The row and column headers are not a part of the matrix Road-Mileage Table Dim rm(3, 3) As Double rm(0,0)=0, rm(0,1)=2054, rm(1,2)=2786

  8. Implicit Array AssignmentRoad-Mileage Dimrm(,) As Double = {{0, 2054, 802, 738}, {2054, 0, 2786, 2706}, {802, 2786, 0, 100}, {738, 2706, 100, 0}} declares and initializes an array of road-mileages.

  9. GetUpperBound Method After execution of the statement DimarrayName(r, c) As varType • the value of arrayName.GetUpperBound(0) is r, • and the value of arrayName.GetUpperBound(1) is c.

  10. Filling a Two-Dimensional Array with a Text File Text File Distances.txt 0,2054,802,738 2054,0,2786,2706 802,2786,0,100 738,2706,100,0 In the next set of code we will read the values of this text file into a two dimensional array.

  11. Filling a Two-Dimensional Array with a Text File (cont.) Dimrm(3, 3) As Double 'road mileage DimrowOfNums() AsString= IO.File.ReadAllLines("Distances.txt") Dimline, data() As String ForiAs Integer = 0To 3 line = rowOfNums(i) data = line.Split(""c) For jAs Integer= 0 To3 rm(i, j) = CDbl(data(j)) Next Next

  12. Outputting Data from a Matrix Private Sub PrintMatrix(rm() as Double) ‘Print a 3 x 3 matrix Dim build as String Forrow As Integer = 0 Torm.getupperbound(0) build = “” Forcol As Integer = 0 Torm.getupperbound(1) build = build &Cstr(rm(row, col)) & “ “ Next lstbox.items.add(build) Next End Sub

  13. Printing a Matrix in Zones 'Print a 3 x 3 matrix Dim rm(,) AsDouble = {{2, 3, 5}, {1, 4, 6}, {0, 7, 9}} Dim frtstr AsString = "{0,-15} {1,-15} {2,-15}" For row AsInteger = 0 To 2 ListBox1.Items.Add(String.Format(frtstr, rm(row, 0), rm(row, 1), rm(row, 2))) Next

  14. Outputting To A DataGridView First create the columns for your matrix

  15. Code For Outputting to a DataGridView Dim example(,) AsInteger = {{1, 2, 3, 4}, {5, 6, 7, 8}, {9, 10, 11, 12}} For r AsInteger = 0 To 2 DataGridView1.Rows.Add() For c AsInteger = 0 To 3 DataGridView1.Item(c, r).Value = example(r, c) Next Next Matrices rows first, columns second DataGridView columns are listed first …Blah

  16. DataGridView Column Headers Dim example(,) AsInteger = {{1, 2, 3, 4}, {5, 6, 7, 8}, {9, 10, 11, 12}} For c AsInteger = 0 To 3 DataGridView1.Columns.Add(CStr(c), "Column " & c) Next For r AsInteger = 0 To 2 DataGridView1.Rows.Add() For c AsInteger = 0 To 3 DataGridView1.Item(c, r).Value = example(r, c) Next Next Column name

  17. DataGridView Row Headers Dim columns() AsString = {"Column1", "Column2", "Column3"} Dim Rows() AsString = {"Row1", "Row2", "Row3"} Dim array2d(,) AsInteger = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}} For c AsInteger = 0 To columns.Count - 1 DataGridView1.Columns.Add(columns(c), columns(c)) Next For r AsInteger = 0 To Rows.Count - 1 DataGridView1.Rows.Add() DataGridView1.Rows(r).HeaderCell.Value = Rows(r) For c AsInteger = 0 To columns.Count - 1 DataGridView1.Item(c, r).Value = array2d(r, c) Next Next 1st Add the row 2nd Assign the row array to the dgv

  18. Processing Each Element Using a For Each Dim nums(,) AsDouble = {{7, 3, 1, 0}, {2, 5, 9, 8}, {0, 6, 4, 10}} 'use a For Each loop Dim total AsDouble = 0 ForEach num AsDoubleIn nums If num Mod 2 = 0 Then total += num EndIf Next lstOutput.Items.Add(total) Finding the sum of the even numbers in a Matrix.

  19. Processing a Matrix Using a LINQ Query Dimnums(,) AsDouble = {{7, 3, 1, 0}, {2, 5, 9, 8}, {0, 6, 4, 10}} 'use a For Each loop 'use LINQ Dim query = FromnumInnums.Cast(OfDouble)() Where (numMod 2 = 0) Selectnum lstOutput.Items.Add(query.Sum)

  20. How do we add up the values in a column? Can you create a For Loop to add up the columns? 2 3 6 8 7 1 4 5 0 2 -2 9 x(0,0) x(0,1) x(0,2) x(0,3) x(0,4) x(1,0) x(1,1) x(1,2) x(1,3) x(1,4) x(2,0) x(2,1) x(2,2) x(2,3) x(2,4)

More Related