This question might be something really simple and I might be missing something really basic, but how do you interpolate a 1D array in C#?
Lets say I have this array of n elements
int[] array1 = new int[] { 1, 3, 5, 7, 1 };
How to stretch or compress the array so that it has n values and interpolates the values, just like when you resize an image, thats it, not chopping or adding zeros or empty values to the array.
For example if I want to convert the array so it has n = 4 elements, get this
array1
>>[2, 4, 6, 4]
what I'm trying to do is the same as the resample function from matlab does
https://mathworks.com/help/signal/ref/resample.html
I suggest this solution for the case that the new array is shorter than the old one:
int[] array1 = new int[] { 1, 3, 5, 7, 9 };
int[] array2 = new int[4];
for (var i = 0; i < array2.Length; i++)
{
var doubleIndex1 = (double)i * array1.Length / array2.Length;
var index1 = (int)Math.Floor(doubleIndex1);
var rel = doubleIndex1 - index1;
array2[i] = (int)Math.Round((1.0 - rel) * array1[index1] + rel * array1[index1 + 1]);
}
im trying to multiply each element in three different arrays by 2 with a loop but im having trouble. im really new at this so please excuse any obvious mistakes lol im not even sure ive im using the right kind of loop but heres what i have so far:
int[] firstArray = new int[] { 1, 2, 5, 6, 9 };
int[] secondArray = new int[] { 12, 3, 8, 20, 7 };
int[] thirdArray = new int[] { 2, 4, 6, 8, 10, 12 };
foreach(new int [5] in firstArray)
{
int newArray1= firstArray.Length * 2;
Console.WriteLine(newArray1);
}
i want it to print out the first new array as "2, 4, 10, 12, 18" in the console but when i run it, i get the error type and identifier are both required in a foreach statement.
any help would be greatly appreciated!
Do this with Linq
int[] resultFirstArray = firstArray.Select(r=> r * 2).ToArray();
int[] resultSecondArray = secondArray.Select(r=> r * 2).ToArray();
int[] resultThirdArray = thirdArray.Select(r=> r * 2).ToArray();
Or you can use Array.ConvertAll
Array.ConvertAll converts an entire array. It converts all elements in one array to another type.
var resultFirstArray = Array.ConvertAll(firstArray, x => 2 * x);
var resultSecondArray = Array.ConvertAll(secondArray, x => 2 * x);
var resultThirdArray = Array.ConvertAll(thirdArray, x => 2 * x);
If you just want to show the doubled values:
foreach(int value in firstArray)
{
Console.WriteLine(2 * value);
}
If you want to double the values in the array, then:
for(int i = 0 ; i < firstArray.Length ; i++)
{
firstArray[i] *= 2;
}
Then perhaps to show those values:
foreach(int value in firstArray)
{
Console.WriteLine(value);
}
If you want to create a new array with the values doubled:
var doubledArray = Array.ConvertAll(firstArray, x => 2 * x);
And to output those values:
foreach(int value in doubledArray)
{
Console.WriteLine(value);
}
given:
int[] myArray = new int[]{-8, -17, 12, 8, 16, -3, 7, 3};
Find all values in array closest to 0.
Currently using another code found on the site but it only tells me 1 value.
int nearest = myArray.Select(p => new {Value = p, Difference = Math.Abs(p - searchValue)}).OrderBy(p => p.Difference).First().Value;
In the current case both -3 and 3 are closest to 0 but since -3 comes first it only outputs -3.
Is there another way to do this where it finds all values instead of just First()?
Just to add to this. If you want to do this using O(n) complexity without sorting then you can do it this way :
public List<int> GetClosestNumbers(int searchVal)
{
int[] myArray = new int[] { -8, -17, 12, 8, 16, -3, 7, 3 };
int minimumDist = int.MaxValue;
List<int> output = new List<int>();
for (int i = 0; i < myArray.Length; i++)
{
var currentDistance = Math.Abs(myArray[i] - searchVal);
if (currentDistance < minimumDist)
{
minimumDist = currentDistance;
output.Clear();
output.Add(myArray[i]);
}
else if (minimumDist == currentDistance)
{
output.Add(myArray[i]);
}
}
return output;
}
Use a grouping on the lowest absolute value
int[] result = myArray
.OrderBy(i => Math.Abs(i - searchValue))
.GroupBy(i => Math.Abs(i - searchValue))
.First()
.ToArray();
Is there any way to do the following?
int[,] multiArray = new int[5,5];
multiArray[0] = {0, 1, 3, 4, 5};
No, with multidimensional arrays, this is not possible. The array has a fixed size, and the compiler does not now what size you are allowed to assign to the array.
Also, how would the compiler know if you meant to do this:
multiArray[0, 0..4] = { 1, 2, 3, 4, 5 };
or this:
multiArray[0..4, 0] = { 1, 2, 3, 4, 5 };
However, you can use jagged arrays:
int[][] multiArray = new int[5][];
multiArray[0] = new[] { 1, 2, 3, 4, 5 };
I think what you want to do is save each element of the array into the same row but DIFFERENT columns of the multiArray.
multiArray[0][0] = 0;
multiArray[0][1] = 1;
multiArray[0][2] = 2;
multiArray[0][3] = 3;
multiArray[0][4] = 4;
multiArray[0][5] = 5;
I believe that is what you're trying to do. You can simplify this with a for loop as well.
Since .NET multidimensional arrays are stored in row-major order, you can use Buffer.BlockCopy for this operation (filling a full row at a time). Note the use of sizeof(int) since this method operates on bytes, not elements (unlike methods such as Array.Copy).
int[,] multiArray = new int[5, 5];
int rowIndex = 0;
int[] rowData = { 0, 1, 3, 4, 5 };
int destOffset = rowIndex * sizeof(int) * multiArray.GetLength(0);
Buffer.BlockCopy(rowData, 0, multiArray, destOffset, rowData.Length * sizeof(int));
Lets say I have this array,
int[] numbers = {1, 3, 4, 9, 2};
How can I delete an element by "name"? , lets say number 4?
Even ArrayList didn't help to delete?
string strNumbers = " 1, 3, 4, 9, 2";
ArrayList numbers = new ArrayList(strNumbers.Split(new char[] { ',' }));
numbers.RemoveAt(numbers.IndexOf(4));
foreach (var n in numbers)
{
Response.Write(n);
}
If you want to remove all instances of 4 without needing to know the index:
LINQ: (.NET Framework 3.5)
int[] numbers = { 1, 3, 4, 9, 2 };
int numToRemove = 4;
numbers = numbers.Where(val => val != numToRemove).ToArray();
Non-LINQ: (.NET Framework 2.0)
static bool isNotFour(int n)
{
return n != 4;
}
int[] numbers = { 1, 3, 4, 9, 2 };
numbers = Array.FindAll(numbers, isNotFour).ToArray();
If you want to remove just the first instance:
LINQ: (.NET Framework 3.5)
int[] numbers = { 1, 3, 4, 9, 2, 4 };
int numToRemove = 4;
int numIndex = Array.IndexOf(numbers, numToRemove);
numbers = numbers.Where((val, idx) => idx != numIndex).ToArray();
Non-LINQ: (.NET Framework 2.0)
int[] numbers = { 1, 3, 4, 9, 2, 4 };
int numToRemove = 4;
int numIdx = Array.IndexOf(numbers, numToRemove);
List<int> tmp = new List<int>(numbers);
tmp.RemoveAt(numIdx);
numbers = tmp.ToArray();
Edit: Just in case you hadn't already figured it out, as Malfist pointed out, you need to be targetting the .NET Framework 3.5 in order for the LINQ code examples to work. If you're targetting 2.0 you need to reference the Non-LINQ examples.
int[] numbers = { 1, 3, 4, 9, 2 };
numbers = numbers.Except(new int[]{4}).ToArray();
You can also convert your array to a list and call remove on the list. You can then convert back to your array.
int[] numbers = {1, 3, 4, 9, 2};
var numbersList = numbers.ToList();
numbersList.Remove(4);
The code that is written in the question has a bug in it
Your arraylist contains strings of " 1" " 3" " 4" " 9" and " 2" (note the spaces)
So IndexOf(4) will find nothing because 4 is an int, and even "tostring" would convert it to of "4" and not " 4", and nothing will get removed.
An arraylist is the correct way to go to do what you want.
I posted my solution here.
This is a way to delete an array element without copying to another array - just in frame of the same array instance:
public static void RemoveAt<T>(ref T[] arr, int index)
{
for (int a = index; a < arr.Length - 1; a++)
{
// moving elements downwards, to fill the gap at [index]
arr[a] = arr[a + 1];
}
// finally, let's decrement Array's size by one
Array.Resize(ref arr, arr.Length - 1);
}
Removing from an array itself is not simple, as you then have to deal with resizing. This is one of the great advantages of using something like a List<int> instead. It provides Remove/RemoveAt in 2.0, and lots of LINQ extensions for 3.0.
If you can, refactor to use a List<> or similar.
Balabaster's answer is correct if you want to remove all instances of the element. If you want to remove only the first one, you would do something like this:
int[] numbers = { 1, 3, 4, 9, 2, 4 };
int numToRemove = 4;
int firstFoundIndex = Array.IndexOf(numbers, numToRemove);
if (numbers >= 0)
{
numbers = numbers.Take(firstFoundIndex).Concat(numbers.Skip(firstFoundIndex + 1)).ToArray();
}
As a generic extension, 2.0-compatible:
using System.Collections.Generic;
public static class Extensions {
//=========================================================================
// Removes all instances of [itemToRemove] from array [original]
// Returns the new array, without modifying [original] directly
// .Net2.0-compatible
public static T[] RemoveFromArray<T> (this T[] original, T itemToRemove) {
int numIdx = System.Array.IndexOf(original, itemToRemove);
if (numIdx == -1) return original;
List<T> tmp = new List<T>(original);
tmp.RemoveAt(numIdx);
return tmp.ToArray();
}
}
Usage:
int[] numbers = {1, 3, 4, 9, 2};
numbers = numbers.RemoveFromArray(4);
You can do in this way:
int[] numbers= {1,3,4,9,2};
List<int> lst_numbers = new List<int>(numbers);
int required_number = 4;
int i = 0;
foreach (int number in lst_numbers)
{
if(number == required_number)
{
break;
}
i++;
}
lst_numbers.RemoveAt(i);
numbers = lst_numbers.ToArray();
' To remove items from string based on Dictionary key values.
' VB.net code
Dim stringArr As String() = "file1,file2,file3,file4,file5,file6".Split(","c)
Dim test As Dictionary(Of String, String) = New Dictionary(Of String, String)
test.Add("file3", "description")
test.Add("file5", "description")
stringArr = stringArr.Except(test.Keys).ToArray()
public int[] DeletePart(int position, params int[] numbers)
{
int[] result = new int[numbers.Length - 1];
int z=0;
for (int i = 0; i < numbers.Length; i++)
{
if (position - 1 != i)
{
result[z] = numbers[i];
z++;
}
}
return result;
}
We can delete array elements by using for loops and continue statements:
string[] cars = {"volvo", "benz", "ford", "bmw"};
for (int i = 0; i < cars.Length; i++)
{
if (cars[i] == "benz")
{
continue;
}
Console.WriteLine(cars[i]);
}