Converting the probability from log-log scale to normal scale
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I need to work in log space because in some cases the denominator gets so small that underflow can happen.I can represent a value with 7 decimals on my computer.
Now the problem is that when i convert these values back to normal scale then i don't get the result what i expect and i don't know if there is any other way to interpret these probabilities.
Example :
double val = Math.log10(5) - Math.log10(10);
System.out.println(Math.exp(val));
I get the output as $0.7400..$.
But the actual probability is $5/10 rightarrow 0.5$. The above value from the logarithmic space is too high.
What i am doing wrong?
logarithms
asked Dec 20 '18 at 17:33
Khan SaabKhan Saab
1979
$endgroup$
add a comment |
$begingroup$
I need to work in log space because in some cases the denominator gets so small that underflow can happen.I can represent a value with 7 decimals on my computer.
Now the problem is that when i convert these values back to normal scale then i don't get the result what i expect and i don't know if there is any other way to interpret these probabilities.
Example :
double val = Math.log10(5) - Math.log10(10);
System.out.println(Math.exp(val));
I get the output as $0.7400..$.
But the actual probability is $5/10 rightarrow 0.5$. The above value from the logarithmic space is too high.
What i am doing wrong?
logarithms
asked Dec 20 '18 at 17:33
Khan SaabKhan Saab
1979
$endgroup$
add a comment |
$begingroup$
I need to work in log space because in some cases the denominator gets so small that underflow can happen.I can represent a value with 7 decimals on my computer.
Now the problem is that when i convert these values back to normal scale then i don't get the result what i expect and i don't know if there is any other way to interpret these probabilities.
Example :
double val = Math.log10(5) - Math.log10(10);
System.out.println(Math.exp(val));
I get the output as $0.7400..$.
But the actual probability is $5/10 rightarrow 0.5$. The above value from the logarithmic space is too high.
What i am doing wrong?
logarithms
asked Dec 20 '18 at 17:33
Khan SaabKhan Saab
1979
$endgroup$
I need to work in log space because in some cases the denominator gets so small that underflow can happen.I can represent a value with 7 decimals on my computer.
Now the problem is that when i convert these values back to normal scale then i don't get the result what i expect and i don't know if there is any other way to interpret these probabilities.
Example :
double val = Math.log10(5) - Math.log10(10);
System.out.println(Math.exp(val));
I get the output as $0.7400..$.
But the actual probability is $5/10 rightarrow 0.5$. The above value from the logarithmic space is too high.
What i am doing wrong?
logarithms
logarithms
asked Dec 20 '18 at 17:33
Khan SaabKhan Saab
1979
asked Dec 20 '18 at 17:33
Khan SaabKhan Saab
1979
asked Dec 20 '18 at 17:33
Khan SaabKhan Saab
1979
asked Dec 20 '18 at 17:33
Khan SaabKhan Saab
1979
asked Dec 20 '18 at 17:33
Khan SaabKhan Saab
1979
1979
add a comment |
add a comment |
1 Answer
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It's because Math.Exp is $e^x$, not $10^x$. Change each log10 to log.
answered Dec 20 '18 at 17:36
J.G.J.G.
28k22844
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$begingroup$
It's because Math.Exp is $e^x$, not $10^x$. Change each log10 to log.
answered Dec 20 '18 at 17:36
J.G.J.G.
28k22844
$endgroup$
add a comment |
$begingroup$
It's because Math.Exp is $e^x$, not $10^x$. Change each log10 to log.
answered Dec 20 '18 at 17:36
J.G.J.G.
28k22844
$endgroup$
add a comment |
$begingroup$
It's because Math.Exp is $e^x$, not $10^x$. Change each log10 to log.
answered Dec 20 '18 at 17:36
J.G.J.G.
28k22844
$endgroup$
It's because Math.Exp is $e^x$, not $10^x$. Change each log10 to log.
answered Dec 20 '18 at 17:36
J.G.J.G.
28k22844
answered Dec 20 '18 at 17:36
J.G.J.G.
28k22844
answered Dec 20 '18 at 17:36
J.G.J.G.
28k22844
answered Dec 20 '18 at 17:36
J.G.J.G.
28k22844
28k22844
add a comment |
add a comment |
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