I'm brand new to flutter and dart. I've searched google and all I can find is how to make 1d lists in flutter. I need a chart of values.
Specifically I need a row 12 long and a column 31 long filled with ascending numbers
1, 32, 63,
2, 33, 64,
3, 34, 65, etc....
thanks!
int row = 3;
int col = 4;
var twoDList = List<List>.generate(row, (i) => List<dynamic>.generate(col, (index) => null, growable: false), growable: false);
//For fill;
twoDList[0][1] = "deneme";
print(twoDList);
// [[null, deneme, null, null], [null, null, null, null], [null, null, null, null]]
Your 2D list having 3 rows and 4 columns.
You can use smart_arrays_numerics package... look at this.. https://pub.dev/packages/smart_arrays_numerics
else you should use nested list.
List<List<int>>
and create your list with generator
Declare and initialize a matrix x having m rows and n columns, containing real numbers.
var x = new List.generate(m, (_) => new List(n));
To get exactly what you want, you could use double List.generate, i.e.:
const cols = 31;
const rows = 12;
final array = List.generate(rows,
(i) => List.generate(cols + 1, (j) => i + j * cols + 1, growable: false),
growable: false);
array.forEach((row) {
print(row);
});
// [1, 32, 63, ...
// [2, 33, 64, ...
// [3, 34, 65, ...
// ...
There is also List.filled, where you can fill the array with some initial value when created. The following init the 2d array with 0s.
final array = List.generate(rows + 1, (i) => List.filled(cols + 1, 0, growable: false), growable: false);
To declare and initialize the array 2D in the dart, you can use:
List<List<int>> a =
[
[10, 2, 4, 6, -2],
[ 1, -16, 6, -2, -5],
[ 0, 3, 10, -5, 1],
[ 0, -4, 1, 18, 2],
[ 3, 1, 2, 2, -14],
];
maybe we can simply create reusable dart code.
void main(List<String> arguments) {
var list = createDimensionList(4, 5);
list[0][0] = 6;
print(list);
list[1][0] = 4;
print(list);
}
List<List<int>> createDimensionList(int rows, int columns,
{bool growable = false}) {
final columnLength = List<int>.filled(columns, 0, growable: growable);
var dataList =
List.generate(rows, (i) => columnLength.toList(), growable: growable);
return dataList;
}
//Output
[[6, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0]]
[[6, 0, 0, 0, 0], [4, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0]]
I would use a nested collection-for:
const maxRows = 31;
const maxColumns = 12;
var matrix = [
for (var row = 0; row < maxRows; row += 1)
[for (var column = 0; column < maxColumns; column += 1)
1 + row + column * maxRows],
];
To initialize a 2d matrix filled with 0 :
List.generate(numberRows, (_) => List.filled(numberColumns, 0));
void main() {
List<dynamic> myArray = nd([12, 31])!;
print(myArray);
}
List? nd(List<int> dimensions) {
if (dimensions.isEmpty) {
return null;
} else {
return List.filled(dimensions[0], nd(dimensions.sublist(1)));
}
}
Just use this statement i got this same problem, Got resolved
var list1 = List.generate(12,(i) => List.generate(31, (j) =>{Your equation to genearte })));
@vahab
so would I do
final int NROWS = 12, NCOLS = 31;
List<Float64List> matrix = List(NROWS);
for (int i = 0; i < 373; i++) {
Float64List row = Float64List(NCOLS);
for (int k = 0; k < NCOLS; k++) { //I dont know what this does
row[k] = double.parse("$i.$k");
}
matrix[i] = row;
}