i was trying to apply filter on grouping function, but i am not getting right syntax. Typically the way we apply filter on grouping function in SQL, i am looking for the same feature or functionality in Pandas.
This is my query, and i want to filter the result where count>=5
home.groupby('location').agg({'price_per_sqft':['mean','std','count']})
Could you show me the way to filter the result?
First for avoid MultiIndex add column price_per_sqft after groupby and then filter by boolean indexing:
df = home.groupby('location')['price_per_sqft'].agg(['mean','std','count'])
df1 = df[df['count']>=5]
Or DataFrame.query:
df1 = df.query("count>=5")
Another idea is used named aggregations:
df = home.groupby('location').agg(avg=('price_per_sqft', 'mean'),
std=('price_per_sqft', 'std'),
counts=('price_per_sqft', 'count'))
df1 = df[df['counts']>=5]
Related
I am getting the daily counts of rows from a dataframe using
df = df.groupby(by=df['startDate'].dt.date).count()
How can I modify this so I can also group by another column 'unitName'?
Thank you
Use list with GroupBy.size:
df = df.groupby([df['startDate'].dt.date, 'unitName']).size()
If need count non missing values, e.g. column col use DataFrameGroupBy.count:
df = df.groupby([df['startDate'].dt.date, 'unitName'])['col'].count()
I have 2 dataframes df1, df2. Both have id as a column. I want to compute a new column, weighted_average, in df1 that is a function of the values in df2 with the same id.
First, I think I should do df1.groupby("id"). Is it possible to use GroupBy.apply(...) and have it use values from df2? In the examples I've seen, it usually just operates on df1 values.
If they have same id positions and length, you can do some like:
df2["new column name"] = df1["column name"].apply(...)
I want to add a new column to a datframe "table" (name: conc) which uses the values in columns (plate, ab) to get the numeric value from the dataframe "concs"
Below is what I mean, with the dataframe "exp" used to show what I expect the data to look like
what is the proper way to do this. Is it using some multiple condition, or do I need to reshape the concs dataframe somehow?
Use DataFrame.melt with left join for new column concs, if no match is created NaNs:
exp = concs.melt('plate', var_name='ab', value_name='concs').merge(table,on=['plate', 'ab'], how='left')
Solution should be simplify - if same columns names 'plate', 'ab' in both DataFrames and need merge by both is possible omit on parameter:
exp = concs.melt('plate', var_name='ab', value_name='concs').merge(table, how='left')
First melt the concs dataframe and then merge with table:
out = concs.melt(id_vars=['plate'],
value_vars=concs.columns.drop('plate').tolist(),
var_name='ab').merge(table, on=['plate', 'ab'
]).rename(columns={'value': 'concs'})
or just make good use of parameters of melt like in jezraels' answer:
out = concs.melt(id_vars=['plate'],
value_name='concs',
var_name='ab').merge(table, on=['plate', 'ab'])
if i have multi-index pivot table like this:
what would be the way to aggregate total 'sum' and 'count' for all dates?
I want to see additional column with totals for all rows in the table.
Thanks to #Nik03 for the idea. The methond of concat returns required data frame but with single index level. To add it to original dataframe, you have to create columns first and assign new dataframes to:
table_to_show = pd.concat([table_to_record.filter(like='sum').sum(1), table_to_record.filter(like='count').sum(1)], axis=1)
table_to_show.columns = ['sum', 'count']
table_to_record['total_sum'] = table_to_show['sum']
table_to_record['total_count'] = table_to_show['count']
column_1st = table_to_record.pop('total_sum')
column_2nd = table_to_record.pop('total_count')
table_to_record.insert(0, 'total_sum', column_1st)
table_to_record.insert(1,'total_count', column_2nd)
and here is the result:
One way:
df1 = pd.concat([df.filter(like='sum').sum(
1), df.filter(like='mean').sum(1)], axis=1)
df1.columns = ['sum', 'mean']
I have some Pandas / cudf code that aggregates a particular column using two aggregate methods, and then renames the multi-index columns to flattened columns.
df = (
some_df
.groupby(["some_dimension"])
.agg({"some_metric" : ["sum", "max"]})
.reset_index()
.rename(columns={"some_dimension" : "some_dimension__id", ("some_metric", "sum") : "some_metric_sum", ("some_metric", "max") : "some_metric_max"})
)
This works great in cudf, but does not work in Pandas 0.25 -- the hierarchy is not flattened out.
Is there a similar approach using Pandas? I like the cudf tuple syntax and how they just implicitly flatten the columns. Hoping to find a similarly easy way to do it in Pandas.
Thanks.
In pandas 0.25.0+ there is something called groupby aggregation with relabeling.
Here is a stab at your code
df = (some_df
.groupby(["some_dimension"])
.agg(some_metric_sum=("some_metric", "sum"),
some_metric_max=("some_metric", "max"]})
.reset_index()
.rename(colunms = {"some_dimension":"some_dimension_id"}))