計算數組的列中的值的平均值？
[英]calculating average of values in column of an array?
問題描述
好的，所以最近我問到如何在Java中訪問數組的各個列，我得到了一個很好的答案。 然后，我打算計算諸如該列中的最大值和平均值之類的值。 但是，我遇到了一個問題。 為了訪問每個值，我假設此列也需要被視為數組。 但是，我訪問每一列的方式是將其存儲為double。 因此，我不知道如何選擇每一列並進行計算。 誰能幫我嗎？ 很抱歉，我在這里發布的內容太多了，看起來似乎什么都沒有，但是我們已經有12周沒有老師了，並且希望通過僅僅自學來完成這項工作，我真的很受困擾。
import java.awt.EventQueue;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.filechooser.FileNameExtensionFilter;
import javax.swing.JTextField;
import javax.swing.JLabel;
import java.awt.Font;
import javax.swing.JButton;
import java.awt.TextArea;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;//Importing any required tools.
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
public class CSVFiles extends JFrame { //Class, inherits properties of the JFrame.
private JPanel contentPane; //Create a container for the GUI.
//Create other components used in the GUI
private JTextField maxTxtVCC;
private JTextField maxTxtTemp;
private JTextField maxTxtLight;
private JTextField minTxtLight;
private JTextField avTxtLight;
private JTextField minTxtTemp;
private JTextField avTxtTemp;
private JTextField minTxtVCC;
private JTextField avTxtVCC;
private JButton btnMax;
private JButton btnMin;
private JButton btnAv;
private JTextField opnTxt;
private JButton btnOpn;
private TextArea textArea;
private JFileChooser fc;
private String content = "";
String [] contentCSV = new String [53000]; //String array to hold the data, 2000 gives more than enough space
int totalValues; //Used to hold the amount of values in the array (52790 ish)
Double[][] values;
double c4, c5, c6;
/**
* Launch the application.
*/
public static void main(String[] args) { //Main method
EventQueue.invokeLater(new Runnable() {
public void run() { //Create a runnable method
try {
CSVFiles frame = new CSVFiles(); //Launch the GUI
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace(); //Print errors
}
}
});
}
/**
* Create the frame.
*/
public CSVFiles() { //Open constructor
super ("CSV Files"); //Create a title for the GUI
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Instruct how the GUI is closed
setBounds(100, 100, 800, 600); //Set size and location
contentPane = new JPanel(); //Declare the JPanel
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5)); //Create a boarder
setContentPane(contentPane); //Add the JPanel
contentPane.setLayout(null); //Set the layout
maxTxtVCC = new JTextField(); //Declare this text field
maxTxtVCC.setBounds(113, 534, 86, 20); //Set size and location
maxTxtVCC.setEditable(false); //Set it so it cannot be edited
contentPane.add(maxTxtVCC); //Add to the content pane
maxTxtTemp = new JTextField(); //Declare this text field
maxTxtTemp.setBounds(113, 503, 86, 20); //Set size and location
maxTxtTemp.setEditable(false); //Set it so it cannot be edited
contentPane.add(maxTxtTemp); //Add to the content pane
maxTxtLight = new JTextField(); //Declare this text field
maxTxtLight.setBounds(113, 472, 86, 20); //Set size and location
maxTxtLight.setEditable(false); //Set it so it cannot be edited
contentPane.add(maxTxtLight); //Add to the content pane
JLabel lblLight = new JLabel("Light"); //Declare this label
lblLight.setFont(new Font("Tahoma", Font.BOLD, 14)); //Set the font and size of text
lblLight.setBounds(22, 469, 46, 17); //Set size and location
contentPane.add(lblLight); //Add to the content pane
JLabel lblTemp = new JLabel("Temperature"); //Declare this label
lblTemp.setFont(new Font("Tahoma", Font.BOLD, 14)); //Set the font and size of text
lblTemp.setBounds(10, 503, 109, 17); //Set size and location
contentPane.add(lblTemp);
JLabel lblVCC = new JLabel("VCC"); //Declare this label
lblVCC.setFont(new Font("Tahoma", Font.BOLD, 14)); //Set the font and size of text
lblVCC.setBounds(22, 534, 46, 17); //Set size and location
contentPane.add(lblVCC); //Add to the content pane
minTxtLight = new JTextField(); //Declare this text field
minTxtLight.setBounds(221, 472, 86, 20); //Set size and location
minTxtLight.setEditable(false); //Set it so it cannot be edited
contentPane.add(minTxtLight); //Add to the content pane
avTxtLight = new JTextField(); //Declare this text field
avTxtLight.setBounds(331, 472, 86, 20); //Set size and location
avTxtLight.setEditable(false); //Set it so it cannot be edited
contentPane.add(avTxtLight); //Add to the content pane
minTxtTemp = new JTextField(); //Declare this text field
minTxtTemp.setBounds(221, 503, 86, 20); //Set size and location
minTxtTemp.setEditable(false); //Set it so it cannot be edited
contentPane.add(minTxtTemp); //Add to the content pane
avTxtTemp = new JTextField(); //Declare this text field
avTxtTemp.setBounds(331, 503, 86, 20); //Set size and location
avTxtTemp.setEditable(false); //Set it so it cannot be edited
contentPane.add(avTxtTemp); //Add to the content pane
minTxtVCC = new JTextField(); //Declare this text field
minTxtVCC.setBounds(221, 534, 86, 20); //Set size and location
minTxtVCC.setEditable(false); //Set it so it cannot be edited
contentPane.add(minTxtVCC); //Add to the content pane
avTxtVCC = new JTextField(); //Declare this text field
avTxtVCC.setBounds(331, 534, 86, 20); //Set size and location
avTxtVCC.setEditable(false); //Set it so it cannot be edited
contentPane.add(avTxtVCC); //Add to the content pane
btnMax = new JButton("Maximum"); //Declare this button
btnMax.setBounds(110, 438, 89, 23); //Set size and location
contentPane.add(btnMax); //Add to the content pane
btnMin = new JButton("Minimum"); //Declare this button
btnMin.setBounds(221, 438, 89, 23); //Set size and location
contentPane.add(btnMin); //Add to the content pane
btnAv = new JButton("Average"); //Declare this button
btnAv.setBounds(328, 438, 89, 23); //Set size and location
contentPane.add(btnAv); //Add to the content pane
textArea = new TextArea(); //Declare this text area
textArea.setBounds(22, 55, 551, 367); //Set size and location
textArea.setEditable(false); //Set it so it cannot be edited
contentPane.add(textArea); //Add to the content pane
btnOpn = new JButton("Open File"); //Declare this button
btnOpn.addActionListener(new ActionListener() { //Add an action listener to this button
public void actionPerformed(ActionEvent arg0) { //Method for action performed
try{
fc = new JFileChooser(); //Declare the file chooser
fc.setFileFilter(new FileNameExtensionFilter("CSV Files", "csv")); //Add a filter for only choosing CSV files
fc.removeChoosableFileFilter(fc.getAcceptAllFileFilter()); //Remove option to select any file type
int returnVal = fc.showOpenDialog(contentPane); // Open the file chooser
File f; //Create a file to hold the data
//If the selected file is approved by the file chooser...
if(returnVal == JFileChooser.APPROVE_OPTION){
f = fc.getSelectedFile(); //Stored selected file into file variable
BufferedReader in = new BufferedReader(new FileReader(f));
StringBuilder builder = new StringBuilder();
String line = "";
textArea.append("Opening "+ f.getAbsolutePath()); //Print out file path
textArea.append("\nLoading file...\n\n"); //Print out loading message and some new lines
in.readLine(); //Skip the first line as it's just headers
int index = 0; //Integer used to label the indexes of the array
while((line = in.readLine()) != null){
builder.append(line);
builder.append("\n");
index++; //increment the index to move the next one up for the next line
String temp[] = line.split(",");
c4 = Double.parseDouble(temp[3]);
c5 = Double.parseDouble(temp[4]);
c6 = Double.parseDouble(temp[5]);
}
totalValues = index; //Set a value to the total values
textArea.append(builder.toString()); //Using the string builder to compile the text
textArea.append("\n*** End of File"); //Print the file onto the text area and an end of file message
in.close(); //Close the reader.
values = new Double [index][3];
}
else{
f = null;
}
}
catch(Exception e){
e.printStackTrace();
}
}
});
btnOpn.setBounds(484, 26, 89, 23); //Set size and location
contentPane.add(btnOpn); //Add to the content pane
opnTxt = new JTextField(); //Declare this text field
opnTxt.setBounds(22, 27, 452, 20); //Set size and location
opnTxt.setEditable(false); //Set it so it cannot be edited
contentPane.add(opnTxt); //Add to the content pane
}
//Methods for Calculations
public static double findMax(double[] array){
double max;
max = array[0];
for(int i=1;i<array.length;++i){
if(array[i]>max){
max = array[i];
}
}
return max;
}
}
另外，在此之后，我嘗試了一種替換代碼，在該代碼中，不是獲取單個列，而是將不需要的列存儲到數組中，以便它們在計算期間被清空，但這也不起作用。 我會非常承認我沒有完全理解這種方法，但是它是基於提供給我們的示例代碼而沒有對其所做的任何解釋，因此我認為我會盡量嘗試。 它在文本區域上顯示文件，但是當我嘗試單擊max按鈕時給出了空指針異常。 http://gyazo.com/27ef7cf9f4bc0c72ecdc3c1f84e6d0f8同樣，請尋求幫助。 我想匆忙一點，因為去年我的課程正在向我求助。因為我在業余時間看了一系列有關Java基礎知識的課程，所以在第一年的工作中沒有遇到麻煩，他們來找我幫助。 但是，我發現沒有Java系列或類似的東西，就像特定的視頻只會有所幫助。 是的，非常感謝您的幫助。 :)
import java.awt.EventQueue;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.filechooser.FileNameExtensionFilter;
import javax.swing.JTextField;
import javax.swing.JLabel;
import java.awt.Font;
import javax.swing.JButton;
import java.awt.TextArea;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;//Importing any required tools.
import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
public class CSVFiles extends JFrame { //Class, inherits properties of the JFrame.
private JPanel contentPane; //Create a container for the GUI.
//Create other components used in the GUI
private JTextField maxTxtVCC;
private JTextField maxTxtTemp;
private JTextField maxTxtLight;
private JTextField minTxtLight;
private JTextField avTxtLight;
private JTextField minTxtTemp;
private JTextField avTxtTemp;
private JTextField minTxtVCC;
private JTextField avTxtVCC;
private JButton btnMax;
private JButton btnMin;
private JButton btnAv;
private JTextField opnTxt;
private JButton btnOpn;
private TextArea textArea;
private JFileChooser fc;
private String content = "";
String [] contentCSV = new String [53000]; //String array to hold the data, 2000 gives more than enough space
int totalValues; //Used to hold the amount of values in the array (52790 ish)
Double[][] values;
/**
* Launch the application.
*/
public static void main(String[] args) { //Main method
EventQueue.invokeLater(new Runnable() {
public void run() { //Create a runnable method
try {
CSVFiles frame = new CSVFiles(); //Launch the GUI
frame.setVisible(true);
} catch (Exception e) {
e.printStackTrace(); //Print errors
}
}
});
}
/**
* Create the frame.
*/
public CSVFiles() { //Open constructor
super ("CSV Files"); //Create a title for the GUI
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //Instruct how the GUI is closed
setBounds(100, 100, 800, 600); //Set size and location
contentPane = new JPanel(); //Declare the JPanel
contentPane.setBorder(new EmptyBorder(5, 5, 5, 5)); //Create a boarder
setContentPane(contentPane); //Add the JPanel
contentPane.setLayout(null); //Set the layout
maxTxtVCC = new JTextField(); //Declare this text field
maxTxtVCC.setBounds(113, 534, 86, 20); //Set size and location
maxTxtVCC.setEditable(false); //Set it so it cannot be edited
contentPane.add(maxTxtVCC); //Add to the content pane
maxTxtTemp = new JTextField(); //Declare this text field
maxTxtTemp.setBounds(113, 503, 86, 20); //Set size and location
maxTxtTemp.setEditable(false); //Set it so it cannot be edited
contentPane.add(maxTxtTemp); //Add to the content pane
maxTxtLight = new JTextField(); //Declare this text field
maxTxtLight.setBounds(113, 472, 86, 20); //Set size and location
maxTxtLight.setEditable(false); //Set it so it cannot be edited
contentPane.add(maxTxtLight); //Add to the content pane
JLabel lblLight = new JLabel("Light"); //Declare this label
lblLight.setFont(new Font("Tahoma", Font.BOLD, 14)); //Set the font and size of text
lblLight.setBounds(22, 469, 46, 17); //Set size and location
contentPane.add(lblLight); //Add to the content pane
JLabel lblTemp = new JLabel("Temperature"); //Declare this label
lblTemp.setFont(new Font("Tahoma", Font.BOLD, 14)); //Set the font and size of text
lblTemp.setBounds(10, 503, 109, 17); //Set size and location
contentPane.add(lblTemp);
JLabel lblVCC = new JLabel("VCC"); //Declare this label
lblVCC.setFont(new Font("Tahoma", Font.BOLD, 14)); //Set the font and size of text
lblVCC.setBounds(22, 534, 46, 17); //Set size and location
contentPane.add(lblVCC); //Add to the content pane
minTxtLight = new JTextField(); //Declare this text field
minTxtLight.setBounds(221, 472, 86, 20); //Set size and location
minTxtLight.setEditable(false); //Set it so it cannot be edited
contentPane.add(minTxtLight); //Add to the content pane
avTxtLight = new JTextField(); //Declare this text field
avTxtLight.setBounds(331, 472, 86, 20); //Set size and location
avTxtLight.setEditable(false); //Set it so it cannot be edited
contentPane.add(avTxtLight); //Add to the content pane
minTxtTemp = new JTextField(); //Declare this text field
minTxtTemp.setBounds(221, 503, 86, 20); //Set size and location
minTxtTemp.setEditable(false); //Set it so it cannot be edited
contentPane.add(minTxtTemp); //Add to the content pane
avTxtTemp = new JTextField(); //Declare this text field
avTxtTemp.setBounds(331, 503, 86, 20); //Set size and location
avTxtTemp.setEditable(false); //Set it so it cannot be edited
contentPane.add(avTxtTemp); //Add to the content pane
minTxtVCC = new JTextField(); //Declare this text field
minTxtVCC.setBounds(221, 534, 86, 20); //Set size and location
minTxtVCC.setEditable(false); //Set it so it cannot be edited
contentPane.add(minTxtVCC); //Add to the content pane
avTxtVCC = new JTextField(); //Declare this text field
avTxtVCC.setBounds(331, 534, 86, 20); //Set size and location
avTxtVCC.setEditable(false); //Set it so it cannot be edited
contentPane.add(avTxtVCC); //Add to the content pane
btnMax = new JButton("Maximum"); //Declare this button
btnMax.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent arg0) {
double tempArray1 [] = new double [totalValues];
double tempArray2 [] = new double [totalValues];
double tempArray3 [] = new double [totalValues];
for (int i = 0; i < totalValues; i++){
tempArray1[i] = values[i][0]; //assign the indexes along side each individual sensor from sensor value
tempArray2[i] = values[i][1];
tempArray3[i] = values[i][2];
}
//execute the method defined in Utils.java to calculate maximum
maxTxtLight.setText(findMax(tempArray1)+"");
maxTxtTemp.setText(findMax(tempArray2)+"");
maxTxtVCC.setText(findMax(tempArray3)+"");
}
});
btnMax.setBounds(110, 438, 89, 23); //Set size and location
contentPane.add(btnMax); //Add to the content pane
btnMin = new JButton("Minimum"); //Declare this button
btnMin.setBounds(221, 438, 89, 23); //Set size and location
contentPane.add(btnMin); //Add to the content pane
btnAv = new JButton("Average"); //Declare this button
btnAv.setBounds(328, 438, 89, 23); //Set size and location
contentPane.add(btnAv); //Add to the content pane
textArea = new TextArea(); //Declare this text area
textArea.setBounds(22, 55, 551, 367); //Set size and location
textArea.setEditable(false); //Set it so it cannot be edited
contentPane.add(textArea); //Add to the content pane
btnOpn = new JButton("Open File"); //Declare this button
btnOpn.addActionListener(new ActionListener() { //Add an action listener to this button
public void actionPerformed(ActionEvent arg0) { //Method for action performed
try{
fc = new JFileChooser(); //Declare the file chooser
fc.setFileFilter(new FileNameExtensionFilter("CSV Files", "csv")); //Add a filter for only choosing CSV files
fc.removeChoosableFileFilter(fc.getAcceptAllFileFilter()); //Remove option to select any file type
int returnVal = fc.showOpenDialog(contentPane); // Open the file chooser
File f; //Create a file to hold the data
//If the selected file is approved by the file chooser...
if(returnVal == JFileChooser.APPROVE_OPTION){
f = fc.getSelectedFile(); //Stored selected file into file variable
BufferedReader in = new BufferedReader(new FileReader(f));
StringBuilder builder = new StringBuilder();
String line = "";
textArea.append("Opening "+ f.getAbsolutePath()); //Print out file path
textArea.append("\nLoading file...\n\n"); //Print out loading message and some new lines
in.readLine(); //Skip the first line as it's just headers
int index = 0; //Integer used to label the indexes of the array
while((line = in.readLine()) != null){
builder.append(line);
builder.append("\n");
index++; //increment the index to move the next one up for the next line
}
totalValues = index; //Set a value to the total values
textArea.append(builder.toString()); //Using the string builder to compile the text
textArea.append("\n*** End of File"); //Print the file onto the text area and an end of file message
in.close(); //Close the reader.
values = new Double [index][3];
for(int i = 0; i < totalValues; i++){
String cols[] = contentCSV[i].split(",");
String tempMillis = cols[0]; //Use a string to take the millis stamp out of the array
String tempStamp = cols[1]; //Use a string to take the time stamp out of the array
String tempDateTime = cols[2]; //Use a string to take the date stamp out of the array
for(int columns=3;columns<cols.length;++columns){
//temp sensor value holds the 9 sensors and the index numbers, parsing the data into double
values[i][columns-3] = Double.parseDouble(cols[columns]);
}
}
}
else{
f = null;
}
}
catch(Exception e){
e.printStackTrace();
}
}
});
btnOpn.setBounds(484, 26, 89, 23); //Set size and location
contentPane.add(btnOpn); //Add to the content pane
opnTxt = new JTextField(); //Declare this text field
opnTxt.setBounds(22, 27, 452, 20); //Set size and location
opnTxt.setEditable(false); //Set it so it cannot be edited
contentPane.add(opnTxt); //Add to the content pane
}
//Methods for Calculations
public static double findMax(double[] array){
double max;
max = array[0];
for(int i=1;i<array.length;++i){
if(array[i]>max){
max = array[i];
}
}
return max;
}
}
1 個解決方案
解決方案1
0 已采納 2014-01-04 13:54:28
問題在這里：
while((line = in.readLine()) != null){
builder.append(line);
builder.append("\n");
index++; //increment the index to move the next one up for the next line
String temp[] = line.split(",");
c4 = Double.parseDouble(temp[3]);
c5 = Double.parseDouble(temp[4]);
c6 = Double.parseDouble(temp[5]);
}
您將值存儲到臨時局部變量（while循環局部變量）中。 這些變量在每個循環中都會重新分配，因此您會丟失信息。
您可以執行以下兩項操作之一：
- 計算運行中的SUM和行數，以便最后計算平均值。 平均值= SUM / COUNT
- 將所有值存儲在arraylist中，最后計算平均值。
例：
double c4avg=0, c5avg=0, c6avg=0;
while((line = in.readLine()) != null){
builder.append(line);
builder.append("\n");
index++; //increment the index to move the next one up for the next line
String temp[] = line.split(",");
//Calculate Running Sum stored in AVG variable
c4avg += Double.parseDouble(temp[3]);
c5avg += Double.parseDouble(temp[4]);
c6avg += Double.parseDouble(temp[5]);
}
//Divide by total rows to get average
c4avg/=index;
c5avg/=index;
c6avg/=index;
從像素數組計算均值/平均值時出現ArrayIndexOutOfBoundsException
[英]ArrayIndexOutOfBoundsException while calculating Mean / Average values from array of pixels
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