I want to find the minimum and the maximum from a matrix from each column. My function
public static void findMinMax(double[][] matrix) {
ArrayList<Double> column = new ArrayList<Double>();
ArrayList<Double> minmax = new ArrayList<Double>();
ArrayList<ArrayList<Double>> minMaxValues = new ArrayList<ArrayList<Double>>();
for (int j=0;j<matrix[1].length;j++) {
column.clear();
minmax.clear();
for (int i=0;i<matrix.length;i++) {
column.add(matrix[i][j]);
}
double max = Collections.max(column);
double min = Collections.min(column);
minmax.add(min);
minmax.add(max);
try {
System.out.println("adding to final minmax " + j);
minMaxValues.add(minmax);
System.out.println(minMaxValues);
} catch (Exception ex) {
System.out.println(ex.getMessage());
}
}
System.out.println(minMaxValues);
}
The problem is that at the last iteration it adds to minMaxValues
only the last minmax
ArrayList. Here is an example of the output
adding to final minmax 0
[[-3.5, 4.5]]
adding to final minmax 1
[[-3.5, 4.5], [-3.5, 4.5]]
adding to final minmax 2
[[-3.5, 4.5], [-3.5, 4.5], [-3.5, 4.5]]
adding to final minmax 3
[[-3.5, 4.2], [-3.5, 4.2], [-3.5, 4.2], [-3.5, 4.2]]
adding to final minmax 4
[[-3.5, 4.2], [-3.5, 4.2], [-3.5, 4.2], [-3.5, 4.2], [-3.5, 4.2]]
adding to final minmax 5
[[-3.5, 4.2], [-3.5, 4.2], [-3.5, 4.2], [-3.5, 4.2], [-3.5, 4.2], [-3.5, 4.2]]
adding to final minmax 6
[[-3.5, 4.2], [-3.5, 4.2], [-3.5, 4.2], [-3.5, 4.2], [-3.5, 4.2], [-3.5, 4.2], [-3.5, 4.2]]
adding to final minmax 7
[[-3.9, 4.2], [-3.9, 4.2], [-3.9, 4.2], [-3.9, 4.2], [-3.9, 4.2], [-3.9, 4.2], [-3.9, 4.2], [-3.9, 4.2]]
adding to final minmax 8
[[-3.9, 4.2], [-3.9, 4.2], [-3.9, 4.2], [-3.9, 4.2], [-3.9, 4.2], [-3.9, 4.2], [-3.9, 4.2], [-3.9, 4.2], [-3.9, 4.2]]
adding to final minmax 9
[[-3.9, 4.2], [-3.9, 4.2], [-3.9, 4.2], [-3.9, 4.2], [-3.9, 4.2], [-3.9, 4.2], [-3.9, 4.2], [-3.9, 4.2], [-3.9, 4.2], [-3.9, 4.2]]
adding to final minmax 10
[[-3.9, 4.5], [-3.9, 4.5], [-3.9, 4.5], [-3.9, 4.5], [-3.9, 4.5], [-3.9, 4.5], [-3.9, 4.5], [-3.9, 4.5], [-3.9, 4.5], [-3.9, 4.5], [-3.9, 4.5]]
As you can see it works fine until minmax 10 where I don't understand what happens. Can anyone help me?
You need to reinitialize ArrayList<Double> minmax
for every iteration. Otherwise your result list will just contain 11 references to the same list , containing the last values that you put in.
You need to move
ArrayList<Double> minmax = new ArrayList<Double>();
inside your loop.
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.