Dav Clark

2016-05-17 22:40:00 UTC

Scopatz already seemingly answered this question here:

https://groups.google.com/forum/#!searchin/pytables-users/sum$20column/pytables-users/1_DV1gC6YIk/KT0tuH4ajdYJ

So, I tried some stuff. None of it works in a way that makes sense. For

example, i have a table in `spy`:

```

# This works and computes what I want, taking a few seconds for something

# I need to do this literally gabillions of times

np.mean(list(x['Bid_Price'] for x in spy.iterrows()))

# These are errors

tb.Expr('sum(spy.cols.Bid_Price)')

tp.Expr('sum(spy["Bid_Price"])')

# So I get the column in a variable:

spy_bp = spy.cols.Bid_Price

# This returns the column - each element

tb.Expr('sum(spy_bp)')

# These are "ValueError: reduction axis is out of bounds"

tb.Expr('sum(spy_bp, axis=0)')

tb.Expr('sum(spy_bp, axis=2)')

# So I can do this...

tb.Expr('sum(spy_bp)').eval().sum()

# But that's bizarre and also slower than the first line above

# This is also slower (but does the same general thing)

tb.Expr('spy_bp').eval().sum()

```

So what was Scopatz suggesting in the above link?

Best,

D

https://groups.google.com/forum/#!searchin/pytables-users/sum$20column/pytables-users/1_DV1gC6YIk/KT0tuH4ajdYJ

So, I tried some stuff. None of it works in a way that makes sense. For

example, i have a table in `spy`:

```

# This works and computes what I want, taking a few seconds for something

# I need to do this literally gabillions of times

np.mean(list(x['Bid_Price'] for x in spy.iterrows()))

# These are errors

tb.Expr('sum(spy.cols.Bid_Price)')

tp.Expr('sum(spy["Bid_Price"])')

# So I get the column in a variable:

spy_bp = spy.cols.Bid_Price

# This returns the column - each element

tb.Expr('sum(spy_bp)')

# These are "ValueError: reduction axis is out of bounds"

tb.Expr('sum(spy_bp, axis=0)')

tb.Expr('sum(spy_bp, axis=2)')

# So I can do this...

tb.Expr('sum(spy_bp)').eval().sum()

# But that's bizarre and also slower than the first line above

# This is also slower (but does the same general thing)

tb.Expr('spy_bp').eval().sum()

```

So what was Scopatz suggesting in the above link?

Best,

D

--

You received this message because you are subscribed to the Google Groups "pytables-users" group.

To unsubscribe from this group and stop receiving emails from it, send an email to pytables-users+***@googlegroups.com.

To post to this group, send an email to pytables-***@googlegroups.com.

For more options, visit https://groups.google.com/d/optout.

You received this message because you are subscribed to the Google Groups "pytables-users" group.

To unsubscribe from this group and stop receiving emails from it, send an email to pytables-users+***@googlegroups.com.

To post to this group, send an email to pytables-***@googlegroups.com.

For more options, visit https://groups.google.com/d/optout.