Reading data with arrays

Programming Questions

bourdonpr..

in Programming Questions • 3 months ago

Hi all.

I load data from a csv file that I visualize afterwards - so far so good. I want then to load another csv data file and I get a Null Pointer Exception, possibly because the new data file has different data entries.

What is the best method to make sure that I don't get this exception? Shall I use try / throw, but I don't know how to create the handling.

Here is some code that I use:

FloatTable data;
Plot[] sensorData;
String fileName;
color[] colorPlot = {
#5679C1, #950095, #F79432
};
float valueX;
int currentColumn = 0;
int columnCount;
//String path = "/Users/Desktop/DataFeedFiles/dataFolder/";
String[] filenames;
ArrayList<String> fileList;
String selectedFile = "1.csv";
int numberOfPlots = 3;
void setup() {
size(800, 480);
loadData();
}
void draw () {
background(200);
println (selectedFile);
//Draw points according to the number of columns that are in the file. Each column
//has one number / point
for (int i=0; i < columnCount; i++) {
sensorData[i].drawDataPoint();
}
}
void loadData(){
File file = new File(selectedFile);
data = new FloatTable(selectedFile);
columnCount = data.getColumnCount();
sensorData = new Plot[numberOfPlots];
for (int i=0; i<numberOfPlots; i++) {
sensorData[i] = new Plot ();
}
}
void keyPressed() {
if (key == 'A' || key == 'a') {
selectedFile = "1.csv";
loadData();
}
if (key == 'S' || key == 's') {
selectedFile = "2.csv";
loadData();
}
}
class FloatTable {
//Based on Ben Fry's class
int rowCount;
int columnCount;
int columnCountSensors;
float[][] data;
String[] rowNames;
String[] columnNames;
String[] columns;
FloatTable(String filename) {
String[] rows = loadStrings(filename);
columns = split(rows[0], ','); //Get columns and set the array
columnNames = subset(columns, 0); // Ignore first columns, get only sensor data
columnCount = columnNames.length; //Get number of columns, i.e. sensor data
rowNames = new String[rows.length-1];
data = new float[rows.length-1][];
for (int i = 1; i < rows.length; i++) {
String[] pieces = split(rows[i], ',');
rowNames[rowCount] = pieces[0]; //Get all the values from column 3, i.e. Minute
data[rowCount] = parseFloat(subset(pieces, 1)); //getColumn except row 1 - header
rowCount++;
}
data = (float[][]) subset(data, 0, rowCount);
}
int getRowCount() {
return rowCount;
}
String getRowName(int rowIndex) {
return rowNames[rowIndex];
}
String[] getRowNames() {
return rowNames;
}
int getRowIndex(String name) {
for (int i = 0; i < rowCount; i++) {
if (rowNames[i].equals(name)) {
return i;
}
}
return -1;
}
int getAllColumnCount() {
return columns.length;
}
int getColumnCount() {
return columnCount;
}
int getColumnCountSensors() {
columnCountSensors = columnCount;
return columnCountSensors;
}
String getColumnName(int colIndex) {
return columnNames[colIndex];
}
String[] getColumnNames() {
return columnNames;
}
float getFloat(int rowIndex, int col) {
if ((rowIndex < 0) || (rowIndex >= data.length)) {
throw new RuntimeException("There is no row " + rowIndex);
}
if ((col < 0) || (col >= data[rowIndex].length)) {
throw new RuntimeException("Row " + rowIndex + " does not have a column " + col);
}
return data[rowIndex][col];
}
boolean isValid(int row, int col) {
if (row < 0) return false;
if (row >= rowCount) return false;
if (col >= columnCount) return false;
if (col >= data[row].length) return false;
if (col < 0) return false;
return !Float.isNaN(data[row][col]);
}
float getTableMin(int colNum) {
float m = Float.MAX_VALUE;
for (int row = 0; row < rowCount; row++) {
//for (int col = 0; col < columnCount; col++) {
//if (isValid(row, col)) {
if (data[row][colNum] < m) {
m = data[row][colNum];
//}
//}
}
}
return m;
}
float getTableMax(int colNum) {
float m = -Float.MAX_VALUE;
for (int row = 0; row < rowCount; row++) {
// for (int col = 0; col < columnCount; col++) {
//if (isValid(row, col)) {
if (data[row][colNum] > m) {
m = data[row][colNum];
//}
//}
}
}
return m;
}
float getColumnMin(int col) {
float m = Float.MAX_VALUE;
for (int i = 0; i < rowCount; i++) {
if (isValid(i, col)) {
if (data[i][col] < m) {
m = data[i][col];
}
}
}
return m;
}
float getColumnMax(int col) {
float m = -Float.MAX_VALUE;
for (int i = 0; i < rowCount; i++) {
if (isValid(i, col)) {
if (data[i][col] > m) {
m = data[i][col];
}
}
}
return m;
}
float getRowMin(int row) {
float m = Float.MAX_VALUE;
for (int i = 0; i < columnCount; i++) {
if (isValid(row, i)) {
if (data[row][i] < m) {
m = data[row][i];
}
}
}
return m;
}
float getRowMax(int row) {
float m = -Float.MAX_VALUE;
for (int i = 0; i < columnCount; i++) {
if (isValid(row, i)) {
if (data[row][i] > m) {
m = data[row][i];
}
}
}
return m;
}
}
class Plot {
//Take csv data and create plots
Plot () {
}
void drawDataPoint() {
fill(#5679C1);
//strokeWeight(1);
//stroke(#5679C1);
beginShape( );
for (int i = 0; i < columnCount; i++) {
float value = data.getFloat(i, 0);
float x = map(i, data.getTableMin(0), data.getTableMax(0), 0, width);
float y = map(value, data.getTableMin(0), data.getTableMax(0), 0, height);
point(x, y);
}
endShape( );
}
}

Replies(2)

tfguy44

Re: Reading data with arrays

3 months ago

This is UNTESTED, meaning I didn't try to run it, but the best way to do this would be something like this:

FloatTable data;
Plot[] sensorData;
Plot[] otherData;
boolean firstData = true;
String fileName;
color[] colorPlot = {
#5679C1, #950095, #F79432
};
float valueX;
int currentColumn = 0;
int columnCount;
//String path = "/Users/Desktop/DataFeedFiles/dataFolder/";
String[] filenames;
ArrayList<String> fileList;
String selectedFile = "1.csv";
int numberOfPlots = 3;
void setup() {
size(800, 480);
loadData(true);
loadData( false );
}
void draw () {
background(200);
//println (selectedFile);
//Draw points according to the number of columns that are in the file. Each column
//has one number / point
for (int i=0; i < columnCount; i++) {
if( firstData ){
sensorData[i].drawDataPoint();
} else {
otherData[i].drawDataPoint();
}
}
}
void loadData( boolean isSecondFile ){
String selectedFile = "1.csv";
if( isSecondFile ) selectedFile = "2.csv";
File file = new File(selectedFile);
data = new FloatTable(selectedFile);
columnCount = data.getColumnCount();
if( !isSecondFile ) sensorData = new Plot[numberOfPlots];
if( isSecondFile ) otherData = new Plot[numberOfPlots];
for (int i=0; i<numberOfPlots; i++) {
if( !isSecondFile ) sensorData[i] = new Plot ();
if( isSecondFile ) otherData[i] = new Plot();
}
}
void keyPressed() {
if (key == 'A' || key == 'a') {
firstData = true;
}
if (key == 'S' || key == 's') {
firstData = false;
}
}
class FloatTable {
//Based on Ben Fry's class
int rowCount;
int columnCount;
int columnCountSensors;
float[][] data;
String[] rowNames;
String[] columnNames;
String[] columns;
FloatTable(String filename) {
String[] rows = loadStrings(filename);
columns = split(rows[0], ','); //Get columns and set the array
columnNames = subset(columns, 0); // Ignore first columns, get only sensor data
columnCount = columnNames.length; //Get number of columns, i.e. sensor data
rowNames = new String[rows.length-1];
data = new float[rows.length-1][];
for (int i = 1; i < rows.length; i++) {
String[] pieces = split(rows[i], ',');
rowNames[rowCount] = pieces[0]; //Get all the values from column 3, i.e. Minute
data[rowCount] = parseFloat(subset(pieces, 1)); //getColumn except row 1 - header
rowCount++;
}
data = (float[][]) subset(data, 0, rowCount);
}
int getRowCount() {
return rowCount;
}
String getRowName(int rowIndex) {
return rowNames[rowIndex];
}
String[] getRowNames() {
return rowNames;
}
int getRowIndex(String name) {
for (int i = 0; i < rowCount; i++) {
if (rowNames[i].equals(name)) {
return i;
}
}
return -1;
}
int getAllColumnCount() {
return columns.length;
}
int getColumnCount() {
return columnCount;
}
int getColumnCountSensors() {
columnCountSensors = columnCount;
return columnCountSensors;
}
String getColumnName(int colIndex) {
return columnNames[colIndex];
}
String[] getColumnNames() {
return columnNames;
}
float getFloat(int rowIndex, int col) {
if ((rowIndex < 0) || (rowIndex >= data.length)) {
throw new RuntimeException("There is no row " + rowIndex);
}
if ((col < 0) || (col >= data[rowIndex].length)) {
throw new RuntimeException("Row " + rowIndex + " does not have a column " + col);
}
return data[rowIndex][col];
}
boolean isValid(int row, int col) {
if (row < 0) return false;
if (row >= rowCount) return false;
if (col >= columnCount) return false;
if (col >= data[row].length) return false;
if (col < 0) return false;
return !Float.isNaN(data[row][col]);
}
float getTableMin(int colNum) {
float m = Float.MAX_VALUE;
for (int row = 0; row < rowCount; row++) {
//for (int col = 0; col < columnCount; col++) {
//if (isValid(row, col)) {
if (data[row][colNum] < m) {
m = data[row][colNum];
//}
//}
}
}
return m;
}
float getTableMax(int colNum) {
float m = -Float.MAX_VALUE;
for (int row = 0; row < rowCount; row++) {
// for (int col = 0; col < columnCount; col++) {
//if (isValid(row, col)) {
if (data[row][colNum] > m) {
m = data[row][colNum];
//}
//}
}
}
return m;
}
float getColumnMin(int col) {
float m = Float.MAX_VALUE;
for (int i = 0; i < rowCount; i++) {
if (isValid(i, col)) {
if (data[i][col] < m) {
m = data[i][col];
}
}
}
return m;
}
float getColumnMax(int col) {
float m = -Float.MAX_VALUE;
for (int i = 0; i < rowCount; i++) {
if (isValid(i, col)) {
if (data[i][col] > m) {
m = data[i][col];
}
}
}
return m;
}
float getRowMin(int row) {
float m = Float.MAX_VALUE;
for (int i = 0; i < columnCount; i++) {
if (isValid(row, i)) {
if (data[row][i] < m) {
m = data[row][i];
}
}
}
return m;
}
float getRowMax(int row) {
float m = -Float.MAX_VALUE;
for (int i = 0; i < columnCount; i++) {
if (isValid(row, i)) {
if (data[row][i] > m) {
m = data[row][i];
}
}
}
return m;
}
}
class Plot {
//Take csv data and create plots
Plot () {
}
void drawDataPoint() {
fill(#5679C1);
//strokeWeight(1);
//stroke(#5679C1);
beginShape( );
for (int i = 0; i < columnCount; i++) {
float value = data.getFloat(i, 0);
float x = map(i, data.getTableMin(0), data.getTableMax(0), 0, width);
float y = map(value, data.getTableMin(0), data.getTableMax(0), 0, height);
point(x, y);
}
endShape( );
}
}

This way all the data is loaded and parsed once for each file, and a control variable is used to determine which set of data is used. This is clunky, but works for 2 files. If you need this to work for many files, use an array of arrays to store the data and a control variable (probably an int, not a boolean) to track which one of the many files is currently being used.

mbraendle

Re: Reading data with arrays

3 months ago

It's perfectly possible to load data in sequence just when it is needed. There is no need to provide different arrays for files with the same type of data (or the same data structure).

Garbage collection of the Java RTE takes care when you reinitialize arrays and update them with the new file data. However, pointers and variables that hold array sizes must be adjusted and HashMaps must be cleared and reinitialized.

So you may have forgotten somewhere in your code to update these (e.g. check rowCount and columnCount).

If one initiates reload of data from outside (via an "API" call), it is advisable to interrupt drawing with noLoop(), then do all the data loading and handling, and then continue with Loop().

As an example, you may have a look at my library navigator code.

The running example is at http://www.clicaps.ethz.ch/librarynavigator/

Upon clicking one of the floor buttons to switch the floor level (either at the left or under the HCI label), new space object data is loaded and displayed.

The source code can be inspected at http://www.clicaps.ethz.ch/librarynavigator/library_space.pde

Although there is much code, the general program path is as follows:

In setup(), initial loading of data using the loadObjectTypes, loadObjects, etc. methods and initialization of arrays and HashMaps.
mousePressed() in the event module does (among other things) call method switch_view() in the class ViewClass.
switch_view() updates the file paths, resets the HashMaps obKey2obIndex and sKey2sIndex and again calls the loadObjects, load... methods.
method update_view() provides an API-type interface for external calls from the AJAX parts in the navigation bar at left. It does a noLoop(), then depending on the type of action passed (e.g. "floor" for a floor switch) does again call switch_view(), then continues drawing with Loop().

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