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

[cklester]

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]

First:

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

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

 

[cklester]

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]

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]

You can use:

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]

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.

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]

Your function produces:

My function produces:

Not the same at all...

 

[LucaMs]

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]

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]

You can use:

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

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

but it will only display 3 decimal places.

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

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

Thank you! I'll look for that.

 

[cklester]

However that routine is slow, that way.

How to make faster?

 

[LucaMs]

How to make faster?

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

 

[cklester]

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]

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]

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.

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]

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]

How to make faster?

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]

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]

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]

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: