how to change specific value in one table based on coordinates listed in second table - dataframe

I have two large csv files (tables).
First file look like this:
row_name
a
b
c
X
1
2
3
Y
1
2
3
Z
1
2
3
Second file looks like this:
a
X
a
Z
b
Y
c
X
c
Z
I need to find value in the first file according the coordinates in the second file to change it to NA.
The result should look like this:
row_name
a
b
c
X
NA
2
NA
Y
1
NA
3
Z
NA
2
NA
I have no experience with this kind of data manipulation, and I am lost for the moment. Can you help me?
I had a look on dplyr package in r, but it did not help. I have no idea how to do it.


With pandas, you can achieve what you want with crosstab and mask :
#pip install pandas
import pandas as pd
df1 = pd.read_csv("tmp/f1.csv", index_col="row_name")
df2 = pd.read_csv("tmp/f2.csv", header=None)
out = df1.mask(pd.crosstab(df2[1], df2[0]).astype(bool), other="NA").reset_index()
​
Output :
print(out)
row_name a b c
0 X NA 2 NA
1 Y 1 NA 3
2 Z NA 2 NA
Input used (.csv files) :

Related

Conditional frequency of elements within lists in pandas data frame

I have a data frame in pandas like this:
STATUS FEATURES
A [x,y,z]
A [t, y]
B [x,p,t]
B [x,p]
I want to count the frequency of the elements in the lists of features conditional on the status.
The desired output would be:
STATUS FEATURES FREQUENCY
A x 1
A y 2
A z 1
A t 1
B x 2
B t 1
B p 2

Let us do explode , the groupby size
s=df.explode(['FEATURES']).groupby(['STATUS','FEATURES']).size().reset_index()

Use DataFrame.explode and SeriesGroupBy.value_counts:
new_df = (df.explode('FEATURES')
.groupby('STATUS')['FEATURES']
.value_counts()
.reset_index(name='FRECUENCY'))
print(new_df)
Output
STATUS FEATURES FRECUENCY
0 A y 2
1 A t 1
2 A x 1
3 A z 1
4 B p 2
5 B x 2
6 B t 1

Pandas groupby sort each group values and order dataframe groups based on max of each group

I have a dataset containing 3 columns, I’m trying to group them and print each group in sorted fashion (based on highest value in each group). The records in each group also have to be in sorted fashion.
Dataset looks like below.
key1,key2,val
b,y,21
c,y,25
c,z,10
b,x,20
b,z,5
c,x,17
a,x,15
a,y,18
a,z,100
df=pd.read_csv('/tmp/hello.csv')
df['max'] = df.groupby(['key1'])['val'].transform('max')
dff=df.sort_values(['max', 'val'], ascending=False).drop('max', axis=1)
I'm applying transform as it works per group basis and then sorting the values.
Above code results in my desired dataframe:
a,z,100
a,y,18
a,x,15
c,y,25
c,x,17
c,z,10
b,y,21
b,x,20
b,z,5
But, the same code fails for below dataset.
key1,key2,val
b,y,10
c,y,10
c,z,10
b,x,2
b,z,2
c,x,2
a,x,2
a,y,2
a,z,2
Below is the desired output
key1,key2,val
c,y,10
c,z,10
c,x,2
b,y,10
b,x,2
b,z,2
a,x,2
a,y,2
a,z,2
Please help me in properly grouping and sorting the dataframe for my scenario.

Add column key1 to sort_values because in second DataFrame are multiple maximum values 10 per groups, so sorting cannot distingush groups:
df['max'] = df.groupby(['key1'])['val'].transform('max')
dff=df.sort_values(['max','key1', 'val'], ascending=False).drop('max', axis=1)
print (dff)
key1 key2 val
8 a z 100
7 a y 18
6 a x 15
1 c y 25
5 c x 17
2 c z 10
0 b y 21
3 b x 20
4 b z 5
df['max'] = df.groupby(['key1'])['val'].transform('max')
dff=df.sort_values(['max','key1', 'val'], ascending=False).drop('max', axis=1)
print (dff)
key1 key2 val
1 c y 10
2 c z 10
5 c x 2
0 b y 10
3 b x 2
4 b z 2
6 a x 2
7 a y 2
8 a z 2

Pandas, multiply part of one DF against another based on condition

Pretty new to this and am having trouble finding the right way to do this.
Say I have dataframe1 looking like this with column names and a bunch of numbers as data:
D L W S
1 2 3 4
4 3 2 1
1 2 3 4
and I have dataframe2 looking like this:
Name1 Name2 Name3 Name4
2 data data D
3 data data S
4 data data L
5 data data S
6 data data W
I would like a new dataframe produced with the result of multiplying each row of the second dataframe against each row of the first dataframe, where it multiplies the value of Name1 against the value in the column of dataframe1 which matches the Name4 value of dataframe2.
Is there any nice way to do this? I was trying to look at using methods like where, condition, and apply but haven't been understanding things well enough to get something working.
EDIT: Use the following code to create fake data for the DataFrames:
d1 = {'D':[1,2,3,4,5,6],'W':[2,2,2,2,2,2],'L':[6,5,4,3,2,1],'S':[1,2,3,4,5,6]}
d2 = {'col1': [3,2,7,4,5,6], 'col2':[2,2,2,2,3,4], 'col3':['data', 'data', 'data','data', 'data', 'data' ], 'col4':['D','L','D','W','S','S']}
df1 = pd.DataFrame(data = d1)
df2 = pd.DataFrame(data = d2)
EDIT AGAIN FOR MORE INFO
First I changed the data in df1 at this point so this new example will turn out better.
Okay so from those two dataframes the data frame I'd like to create would come out like this if the multiplication when through for the first four rows of df2. You can see that Col2 and Col3 are unchanged, but depending on the letter of Col4, Col1 was multiplied with the corresponding factor from df1:
d3 = { 'col1':[3,6,9,12,15,18,12,10,8,6,4,2,7,14,21,28,35,42,8,8,8,8,8,8], 'col2':[2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2], 'col3':['data','data','data','data','data','data','data','data','data','data','data','data','data','data','data','data','data','data','data','data','data','data','data','data'], 'col4':['D','D','D','D','D','D','L','L','L','L','L','L','D','D','D','D','D','D','W','W','W','W','W','W']}
df3 = pd.DataFrame(data = d3)

I think I understand what you are trying to achieve. You want to multiply each row r in df2 with the corresponding column c in df1 but the elements from c are only multiplied with the first element in r the rest of the row doesn't change.
I was thinking there might be a way to join df1.transpose() and df2 but I didn't find one.
While not pretty, I think the code below solves your problem:
def stretch(row):
repeated_rows = pd.concat([row]*len(df1), axis=1, ignore_index=True).transpose()
factor = row['col1']
label = row['col4']
first_column = df1[label] * factor
repeated_rows['col1'] = first_column
return repeated_rows
pd.concat((stretch(r) for _, r in df2.iterrows()), ignore_index=True)
#resulting in
col1 col2 col3 col4
0 3 2 data D
1 6 2 data D
2 9 2 data D
3 12 2 data D
4 15 2 data D
5 18 2 data D
0 12 2 data L
1 10 2 data L
2 8 2 data L
3 6 2 data L
4 4 2 data L
5 2 2 data L
0 7 2 data D
1 14 2 data D
2 21 2 data D
3 28 2 data D
4 35 2 data D
5 42 2 data D
0 8 2 data W
1 8 2 data W
2 8 2 data W
3 8 2 data W
4 8 2 data W
5 8 2 data W
...

Pandas: Imputing Missing Values to Data Frame

Suppose I have a data frame with some missing values, as below:
import pandas as pd
df = pd.DataFrame([[1,3,'NA',2], [0,1,1,3], [1,2,'NA',1]], columns=['W', 'X', 'Y', 'Z'])
print(df)
The variable Y is missing two values. Say I run some imputation model and come up with an estimate of what the two values should be:
to_impute = [2,1]
What is the best way of replacing the two NA's with those two values? I know of ways that are fairly roundabout, e.g. looping over to_impute and using df.iloc to add each value. But I'm hoping there is a concise and non-iterative way.
(This is something that is easy in R, and I'm hoping it can be easy in Pandas.)

In pandas NA should be NaN, 1st you need to replace it , then we can using fillna
df.Y=df.Y.replace('NA',np.nan)
df.Y=df.Y.fillna(pd.Series([1,2],index=df.index[df.Y.isnull()]))
df
Out[1375]:
W X Y Z
0 1 3 1.0 2
1 0 1 1.0 3
2 1 2 2.0 1
Let us treat your NA as str
df.loc[df.Y=='NA','Y']=[1,2]
df
Out[1380]:
W X Y Z
0 1 3 1 2
1 0 1 1 3
2 1 2 2 1

Calculating Growth-Rates by applying log-differences

I am trying to transform my data.frame by calculating the log-differences of each column
and controlling for the rows id. So basically I like to calculate the growth rates for each id's variable.
So here is a random df with an id column, a time period colum p and three variable columns:
df <- data.frame (id = c("a","a","a","c","c","d","d","d","d","d"),
p = c(1,2,3,1,2,1,2,3,4,5),
var1 = rnorm(10, 5),
var2 = rnorm(10, 5),
var3 = rnorm(10, 5)
)
df
id p var1 var2 var3
1 a 1 5.375797 4.110324 5.773473
2 a 2 4.574700 6.541862 6.116153
3 a 3 3.029428 4.931924 5.631847
4 c 1 5.375855 4.181034 5.756510
5 c 2 5.067131 6.053009 6.746442
6 d 1 3.846438 4.515268 6.920389
7 d 2 4.910792 5.525340 4.625942
8 d 3 6.410238 5.138040 7.404533
9 d 4 4.637469 3.522542 3.661668
10 d 5 5.519138 4.599829 5.566892
Now I have written a function which does exactly what I want BUT I had to take a detour which is possibly unnecessary and can be removed. However, somehow I am not able to locate
the shortcut.
Here is the function and the output for the posted data frame:
fct.logDiff <- function (df) {
df.log <- dlply (df, "code", function(x) data.frame (p = x$p, log(x[, -c(1,2)])))
list.nalog <- llply (df.log, function(x) data.frame (p = x$p, rbind(NA, sapply(x[,-1], diff))))
ldply (list.nalog, data.frame)
}
fct.logDiff(df)
id p var1 var2 var3
1 a 1 NA NA NA
2 a 2 -0.16136569 0.46472004 0.05765945
3 a 3 -0.41216720 -0.28249264 -0.08249587
4 c 1 NA NA NA
5 c 2 -0.05914281 0.36999681 0.15868378
6 d 1 NA NA NA
7 d 2 0.24428771 0.20188025 -0.40279188
8 d 3 0.26646102 -0.07267311 0.47041227
9 d 4 -0.32372771 -0.37748866 -0.70417351
10 d 5 0.17405309 0.26683625 0.41891802
The trouble is due to the added NA-rows. I don't want to collapse the frame and reduce it, which would be automatically done by the diff() function. So I had 10 rows in my original frame and am keeping the same amount of rows after the transformation. In order to keep the same length I had to add some NAs. I have taken a detour by transforming the data.frame into a list, add the NAs to each id's first line, and afterwards transform the list back into a data.frame. That looks tedious.
Any ideas to avoid the data.frame-list-data.frame class transformation and optimize the function?

How about this?
nadiff <- function(x, ...) c(NA, diff(x, ...))
ddply(df, "code", colwise(nadiff, c("var1", "var2", "var3")))