I have some code that has heavy use of arrays. It all works but there are many for loops where I iterate and copy contents from several arrays to a new array with more dimensions to fit all content.
As I understand it, there is no way to do this without a for loop (to copy array content to another array). Is this correct?
There is the method Array.Copy(arSource,arTarget,length). But it does not work with more dimensions arrays. The new one is that jagged arrays()arrays of arrays are more perfomant than 2D ARRAYS,if you move along the vectors.
Related
I have an array of type Double() (1 x n) that I am trying to quickly plot on a graph I've already set up. The only thing I want/need to do is take my array and store it as data points (y-axis values) in the series I already have. What's the best way to do this? Also, will the data points that are plotted change as my array changes, and if not, how would I replot those new points and get rid of the old points?
Adding the points should be as simple as
Chart1.Series("Default").Points.Add(arrayName)
As for it being auto-updated when you change the array, I believe if you just add the points, you are going to have an issue like pee in a swimming pool (once they are in there, you can't get them out). So, you add an array with 3 items, then add a double to the array, then the add to the chart again, you now incorrectly have 7 points. However, you can databind the array to the series, like so.
Chart1.Series("Default").Points.DataBindXY(xStrings, xDoubles)
In this case, if the array changes, the chart should change as well.
I am trying to populate a number of UITextFields with data. Currently, I am doing it line-by-line.
myFirstName.text = originalPerson.firstname ;
myLastName.text = originalPerson.lastname;
myAddress1.text = originalPerson.address1;
Is there a way to do it programatically, in a loop?
You could add your text fields to an array (or IBOutletCollection), and your keys to another array, and then in your loop assign the value for the key in your array to the equivalent text field in your other array, but by the time you've done and maintained and debugged all that, I don't think you'll have saved yourself much.
I have EuroCPCrap mapped as (j,0)(i,0) and want to put this into an array EuroCPConsol mapped as (j,i). I tried:
For j = 0 to CPIndex 'CPIndex is a global count of variables in matrix j references
For i = 0 to UBound (EuroCPCrap,3) 'i in the (now known to be) jagged
EuroCPConsol(j+1,i+1)= EuroCPCrap(j,0,i,0) 'add one since I'm base 1 but function that produced this matrix outputted base zero
Next i
Next j
I get a subscript error on the UBound statement, and I realised it's because there is no 3rd dimension in the referenced array.
First of all, I don't understand why this EuroCPCrap(j,0,i,0) would work if it's a jagged array as you describe in your first sentence. On the looks of it, it should be EuroCPCrap(j,0)(i,0).
You have a parent two-dimensional array of children two-dimensional arrays. The "third" dimension you're looking for is actually the first dimension of each child array. So something like this should work:
For i = 0 to UBound(EuroCPCrap(j,0),1)
Actually, iterating from LBound to UBound is even better practice to ensure that the entire array is traversed regardless of your Option Base or how the array is "Dimmed":
For i = LBound(EuroCPCrap(j,0),1) to UBound(EuroCPCrap(j,0),1)
Does EuroCPCrap really need to be jagged? Why not make it a 4-dimensional array? EuroCPConsol is not jagged... Is it dimensioned correctly to accept the contents of the largest of the children array? These are things to think about...
I have an array variable (string type). It contains certain no. of items, that I donot know how many they are.
I need to run a loop for that many nos. that the array contains. I tried LBound and UBound loop but it says my array is not a system array.
How can I know how many items my array contains?
Thanks
Furqan
You can use the Length property of the array object.
From MSDN (Array.Length Property):
Gets a 32-bit integer that represents the total number of elements in all the dimensions of the Array.
Read about arrays in VB.NET and the Array class for better understanding of arrays in VB.NET and the .NET framework.
Update:
However, for looping over an array you should simply use a For Each loop (as an array is treated like any other collection in .NET) - this way you will not make any silly mistakes with array bounds and off by ones:
For Each item As arrayItemType in MyArray
' do stuff with item
Next
See the example on this page.
You look at the length:
To get the number of items in the first dimension: arrayName.GetLength(0)
If you need the index, use GetUpperBound(0)
Some helpful examples here.
Like Oded said, you can use the Length-propery of the Array. This would look something like this:
Dim data As String() = {"one", "two", "three", "four"}
For i = 0 To data.Length - 1
Console.WriteLine(data(i))
Next
If you just want to loop all strings in your array, you can use For Each as well:
For Each s As String In data
Console.WriteLine(s)
Next
If the compiler is telling you that your variable is not a system array, then chances are, it's not an array. If it's not an array, you won't be able to get its bounds through any means.
Inspect the variable in the locals window and verify that your variable is of the type that you think it is. It's probably not an array after all.
How can I resize the two dimensional array size without affecting its value?
Use ReDim with the Preserve modifier. VB.NET will make sure the original values are untouched. Didn't read the documentation right. ReDim Preserve will only allow you to change the length of the last dimension of the array.
You need to allocate a new array (with the correct size) and manually copy the elements from the first array to the second.
As Adam said, you can't resize 2D arrays dynamically. You can easily copy the existing array into a bigger one like so:
Dim smaller(1, 1) As Byte
Dim bigger(2, 2) As Byte
Array.Copy(smaller, bigger, smaller.length)
Try using array.resize if you are on .net 2 framework or above.
For example:
Dim MyArray() as string
Array.Resize(myarray,12)