This is my SQL:
SELECT st_asText(ST_GeomFromText('POINT(52.000000000012345678 21.0000000000123456789)'))
SELECT st_asText(ST_MakePoint(52.000000000012345678, 21.0000000000123456789))
But response is:
POINT(52.0000000000123 21.0000000000123)
I need double double precision in PostGis. How can i fix it?
That is already double precision. Single precision coordinates would trim after the sixth decimal whereas double offers 15 digits of precision. You're trying to set a point with 18 decimal positions.
Also is important to note that the number of decimal places a double can hold depends on the numbers to the left of the decimal separator. (see OSGeo rants abot that) so you're using two digits for the integer part (52 and 21) and you have 13 digits left to play with, which is exactly what you're getting in the response.
Related
I defined a column in my schema named location POINT NOT NULL. The point class specifies X- and Y-coordinate values. How many decimal places can these X and Y values have? I cannot find an exact definition – especially for the fractional part – for these properties.
MySQL stores the spacial datatypes in the WKB format.
This format uses double precision to store the X and Y co-ordinates. This means that it can store a precision of 16 decimal digits (53 bits of precision)
More information on double precision float format here
Can I generate a custom data type in postgres that everytime I insert or update a float into it it is truncate to 2 decimals after dot.
create table money(
formatted moneys_type
);
insert into money values (30.122323213);
Select * from money;
Returns
30.12
Update I didn't use numeric or decimal because they round up when 1.999 => 2
See documentation on Numeric Types / Arbitrary Precision Numbers.
The precision of a numeric is the total count of significant digits in
the whole number, that is, the number of digits to both sides of the
decimal point. The scale of a numeric is the count of decimal digits
in the fractional part, to the right of the decimal point. So the
number 23.5141 has a precision of 6 and a scale of 4. Integers can be
considered to have a scale of zero.
...
To declare a column of type numeric use the syntax:
NUMERIC(precision, scale)
The maximum allowed precision when explicitly specified in the type declaration is 1000.
So you can use
NUMERIC(1000, 2)
I'm using postgres sql I need 12 digits and after decimal I need only 6 digits what length & Precision should I give in columns.what datatype shold I give to cloumn.
I tried numeric as a datatype and length I give to column is 12 and precision is 6.
If you need 12 digits before the decimal and 6 digits after, you need numeric(18,6)
Quote from the manual
The scale of a numeric is the count of decimal digits in the fractional part, to the right of the decimal point. The precision of a numeric is the total count of significant digits in the whole number, that is, the number of digits to both sides of the decimal point
(Emphasis mine)
So the first number (precision) in the type definition is the total number of digits. The second one is the number of decimal digits.
If you specify numeric(12,6) you have a total of 12 digits and 6 decimal digits, which leaves you only 6 digits for the digits to the left of the decimal. Therefor you need numeric(18,6)
I am reading some data from a CSV file, and I have custom code to parse string values into different data types. For numbers, I use:
val format = NumberFormat.getNumberInstance()
which returns a DecimalFormat, and I call parse function on that to get my numeric value. DecimalFormat has arbitrary precision, so I am not losing any precision there. However, when the data is pushed into a Spark DataFrame, it is stored using DoubleType. At this point, I am expecting to see some precision issues, however I do not. I tried entering values from 0.1, 0.01, 0.001, ..., 1e-11 in my CSV file, and when I look at the values stored in the Spark DataFrame, they are all accurately represented (i.e. not like 0.099999999). I am surprised by this behavior since I do not expect a double value to store arbitrary precision. Can anyone help me understand the magic here?
Cheers!
There are probably two issues here: the number of significant digits that a Double can represent in its mantissa; and the range of its exponent.
Roughly, a Double has about 16 (decimal) digits of precision, and the exponent can cover the range from about 10^-308 to 10^+308. (Obviously, the actual limits are set by the binary representation used by the ieee754 format.)
When you try to store a number like 1e-11, this can be accurately approximated within the 56 bits available in the mantissa. Where you'll get accuracy issues is when you want to subtract two numbers that are so close together that they only differ by a small number of the least significant bits (assuming that their mantissas have been aligned shifted so that their exponents are the same).
For example, if you try (1e20 + 2) - (1e20 + 1), you'd hope to get 1, but actually you'll get zero. This is because a Double does not have enough precision to represent the 20 (decimal) digits needed. However, (1e100 + 2e90) - (1e100 + 1e90) is computed to be almost exactly 1e90, as it should be.
If I set a variable in Matlab, say var1 = 2.111, after running the script, Matlab returns var1 = 2.1110. I want Matlab to return the original number, with no trailing zero. Anyone know how to do this. Thanks in advance.
By default Matlab displays results in Short fixed decimal format, with 4 digits after the decimal point.
You can change that to various other format such as:
long
Long fixed decimal format, with 15 digits after the decimal point for double values, and 7 digits after the decimal point for single values.
3.141592653589793
shortE
Short scientific notation, with 4 digits after the decimal point.
Integer-valued floating-point numbers with a maximum of 9 digits do not display in scientific notation.
3.1416e+00
longE
Long scientific notation, with 15 digits after the decimal point for double values, and 7 digits after the decimal point for single values.
Integer-valued floating-point numbers with a maximum of 9 digits do not display in scientific notation.
3.141592653589793e+00
shortG
The more compact of short fixed decimal or scientific notation, with 5 digits.
3.1416
longG
The more compact of long fixed decimal or scientific notation, with 15 digits for double values, and 7 digits for single values.
3.14159265358979
shortEng
Short engineering notation, with 4 digits after the decimal point, and an exponent that is a multiple of 3.
3.1416e+000
longEng
Long engineering notation, with 15 significant digits, and an exponent that is a multiple of 3.
3.14159265358979e+000
However I don't think other options are available. If you absolutely want to remove those zeros you would have to cast you result in a string and remove the trailing 0 characters and then display your result as a string and not a number.