At 11:56 AM 8/3/2013, drfg2008 wrote:
>how many decimal places does SPSS accept in the data sheet?
>
>Example from a csv file:
>
>var1;var2;var3
>1.123456789123456789123456789123456789;1.123456789123456789123456789123456789;1.123456789123456789123456789123456789
>
>SPSS reads it as STRING. Then by trying to convert it into Numeric
>(ALTER TYPE var1 to var3 (F30.28).) it gives an error message.
SPSS stores numeric data in binary with 53 bits precision, slightly
less than 16 decimal digits.
What that means for you depends on how the long numbers arise in your
work, and what you need to do with them. For example,
. They may be identifiers, and not need to be processed numerically.
For that, retaining them as strings may suffice -- though, using any
non-integer numeric value as an identifier is dangerous, and you
should be careful of truncation or rounding errors in the low-order digits.
. The actual values you need to work with may be differences between
these high-precision values, or differences from same base value, and
the differences may have lower precision, within SPSS's
representation range. If so, you may be able to calculate the
differences in your source system, and read only the differences into
SPSS; or, harder but not impossible, read the numbers into SPSS as
strings, and write what amounts to multiple-precision code in SPSS to
calculate the differences.
. You really may have values with extremely high precision. In that
case, you may not be able to use SPSS (or other standard software
packages, as most use the same numeric representation); but that will
depend on what you need to compute from the values.
So, please fill us in a little more on your needs.
(And, if you're pushing the limits of SPSS's precision, remember:
most statistical computations are not accurate to full machine
precision. Algorithms have improved in recent years, and SPSS's are
probably pretty good, but do not count on accuracy reaching, or even
closely approaching, the full 53 bits.)
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