B4J Question [SOLVED] How To Get Precise B4XTable Column Numbers

cklester · Nov 30, 2021

Check out the attached simple B4XTable app.

The numbers in each column come from the same source, but they are often displayed as two wildly different numbers!

Can anybody explain why, and how I can make sure that any numbers I display with COLUMN_TYPE_NUMBERS are as precise as can be?

I'm not sure if it's the MyNumberString.As(Float) that is problematic, or B4XTable munging the numbers.

Who knows?

This has been resolved with the use of a column formatter (B4XFormatter). Check out the attached app to see how it works.

There's also a random number generator that gets you anything from "0.0" to "999999999.999999999." It's handy for testing purposes. (Might could be made faster, but it's already fast enough.)

LucaMs · Nov 30, 2021

First:

Your function:

Public Sub randomStringOfNumbers(len As Int) As String
    Dim numbers As String = "0123456789"
    Dim theNum As StringBuilder
    theNum.Initialize
    Dim numChars As Int = Rnd(1, len)
    Dim i As Int
    For i=0 To numChars-1
        theNum.Append(numbers.CharAt(Rnd(0,numbers.Length-1)))
    Next
    Return theNum
End Sub

More simple:

Public Sub randomStringOfNumbers(len As Int) As String
    Return "0123456789".SubString2(0, len)
End Sub

cklester · Nov 30, 2021

LucaMs said:

More simple:

Public Sub randomStringOfNumbers(len As Int) As String
    Return "0123456789".SubString2(0, len)
End Sub

Sure... For this test, that would suffice, but for a random string of numbers, it would not suffice. ?

LucaMs · Nov 30, 2021

cklester said:
Sure... For this test, that would suffice, but for a random string of numbers, it would not suffice.

I don't understand what you mean; the two functions do the exact same job, they return the same result.

If you want to create random numbers, this has nothing to do with the simplification I suggested.

LucaMs · Nov 30, 2021

You can use:

B4X:

allTheRows.Add(Array(theValue, theValue.As(Double)))

but it will only display 3 decimal places.
To get exactly what you want, you should use B4XFormatter for that column.

cklester · Nov 30, 2021

LucaMs said:
I don't understand what you mean; the two functions do the exact same job, they return the same result.

Huh? They don't produce the same result at all.

Your function could never return a number like "4859.33392" whereas mine could.

Your function returns random-length numbers that ALWAYS start with "0".

Mine produces a random-length string numbers of random numbers.

LucaMs said:
If you want to create random numbers, this has nothing to do with the simplification I suggested.

The whole point of the function I posted is to create a random-length string of random numbers.

cklester · Nov 30, 2021

Your function produces:

My function produces:

Not the same at all...

LucaMs · Nov 30, 2021

cklester said:
Huh? They don't produce the same result at all.

Your function could never return a number like "4859.33392" whereas mine could.

Your function returns random-length numbers that ALWAYS start with "0".

Mine produces a random-length string numbers of random numbers.

The whole point of the function I posted is to create a random-length string of random numbers.

Yes, I realized they were random; I've seen them consecutive! (distracted).

However that routine is slow, that way.

LucaMs · Nov 30, 2021

The only way to get exactly what you want is to use B4XFormatter; unless you also set the second column as text and use NumberFormat2.

cklester · Nov 30, 2021

LucaMs said:
You can use:

B4X:

allTheRows.Add(Array(theValue, theValue.As(Double)))

I thought a double was an int... (didn't help anyway)

LucaMs said:
but it will only display 3 decimal places.

Ah... So is that a limitation of the basic B4XTable?

LucaMs said:
To get exactly what you want, you should use B4XFormatter for that column.

Thank you! I'll look for that.

cklester · Nov 30, 2021

LucaMs said:
However that routine is slow, that way.

How to make faster? ?

LucaMs · Nov 30, 2021

cklester said:
How to make faster? ?

By using 2 number variables and NumberFormat2 to "join" them.

cklester · Nov 30, 2021

LucaMs said:
The only way to get exactly what you want is to use B4XFormatter; unless you also set the second column as text and use NumberFormat2.

I'm getting the number as a string, so NumberFormat2 doesn't help. I'd like to have them as numbers so they sort properly, so I'll look into the B4XFormatter.

Thank you!

LucaMs · Nov 30, 2021

cklester said:
I'm getting the number as a string, so NumberFormat2 doesn't help.

I meant in your randomStringOfNumbers, which returns a string.

But you cannot insert a string-number in a numeric column and be able to obtain the desired formatting.
The number to insert must be... a number (better a Double) and then format it using B4XFormatter.

cklester · Nov 30, 2021

LucaMs said:
I meant in your randomStringOfNumbers, which returns a string.

Yes, but there's never an actual number (float, double, etc.)... The number sent to the function determines the maximum length of the string of random digits.

LucaMs said:
But you cannot insert a string-number in a numeric column and be able to obtain the desired formatting.
The number to insert must be... a number (better a Double) and then format it using B4XFormatter.

I take the string generated by the function and turn it into a float to insert into the B4XTable, so there is an Array of Object(string, float) being put into the B4XTable. i.e., there is no string being put into a number column. It's all done properly.

The problem was, it looks like the format of the column is limited to three decimal places or 8-9 digits in length.

LucaMs · Nov 30, 2021

cklester said:
Yes, but there's never an actual number (float, double, etc.)... The number sent to the function determines the maximum length of the string of random digits.

I take the string generated by the function and turn it into a float to insert into the B4XTable, so there is an Array of Object(string, float) being put into the B4XTable. i.e., there is no string being put into a number column. It's all done properly.

The problem was, it looks like the format of the column is limited to three decimal places or 8-9 digits in length.

They are certainly default values; 3 decimals for double values, I suppose.

However, you also want to get a fixed length for the whole part, don't you? Also for this you will need B4XFormatter.

LucaMs · Nov 30, 2021

cklester said:
How to make faster? ?

B4X:

Public Sub randomStringOfNumbers(len As Int) As String
    Dim Left As Int = Rnd(0, Power(10, len))
    Dim Right As Int = Rnd(0, Power(10, len))
    Return NumberFormat2(Left, len, 0, 0, False) & "." & NumberFormat2(Right, len, 0, 0, False)
End Sub

cklester · Nov 30, 2021

LucaMs said:
However, you also want to get a fixed length for the whole part, don't you? Also for this you will need B4XFormatter.

Eventually, I'd like to line up the decimal in the column, but I'm taking baby steps... ?

The column has to be numbers, because otherwise it won't sort properly. Unless I can specify somewhere for strings to sort like numbers!

LucaMs · Nov 30, 2021

I don't know the final purpose. Theoretically you could set that column as text and pass it numbers formatted with NumberFormat2. It would be the simplest solution.

But learning B4XFormatter is also helpful.

cklester · Nov 30, 2021

LucaMs said:
Theoretically you could set that column as text and pass it numbers formatted with NumberFormat2.

Unfortunately, I couldn't. The way it sorts string numbers is problematic. Here's the table with the text-numbers sorted:

B4J Question [SOLVED] How To Get Precise B4XTable Column Numbers

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