Using Dataframes style.apply for Highlighting based on comparative values

Question

In my code I am using df.style.applymap() to render HTML onto my intranet Webpage. I have the following Code which is working Well for me, (2 Columns are passed on to my function highlight_vals).

def highlight_vals(val, color='green', color1='red'):
        if val > 0.8:
            return 'background-color: %s' % color
        elif val < -0.9:
            return 'background-color: %s' % color1
        else:
            return ''

Now, I want to make a similar function (or ever use the current highlight_vals) in order to achieve Comparative Highlighting with the condition on the lines of:
if ValinColumn1 > 0.25 * ValinColumn2: # (For same Row/Record)
return 'background-color: %s' % color #Yellow/Highlights.

I am using the above function in my views.py:
httresp += df.style.applymap(highlight_vals,subset=[col1,col2])

score 5 · Answer 1 · answered Sep 27 '18 at 05:10

5

You need to use apply(axis=1) to iterate through rows:

def highlight_vals(row, cols=['A', 'B'], color='green'):
    a, b = cols
    styles = {col: '' for col in row.index}
    if row[a] > 0.25 * row[b]:
        styles[a] = 'background-color: %s' % color
        styles[b] = 'background-color: %s' % color
    return styles

df.style.apply(lambda x: highlight_vals(x, cols=['B', 'E']), axis=1)

answered Sep 27 '18 at 05:10

hellpanderr

5,581
3
33
43

Thank You, I will test this out sometime today. – Suraj_j Sep 27 '18 at 07:50
I checked this in detail, it appears to be Highlighting the wrong columns, Do we really need to use the Lambda here, the Pandas Documentation suggests otherwise. – Suraj_j Sep 30 '18 at 03:38
It appears the cols is not working in the Function Highlight_vals – Suraj_j Sep 30 '18 at 03:50
Well firstly I am able to same result as above using just apply(highlight_vals, axis=1), i.e. I am Not using the Lambda – Suraj_j Sep 30 '18 at 09:47
However with your original code and my code it still the Wrong column gets Highlighted , the condition itself is fine. – Suraj_j Sep 30 '18 at 09:47
Thanks for the Help though, currently I am fine with this solution. – Suraj_j Sep 30 '18 at 09:53
Just to be clear Your code as well as my revised code just Highlight the First column (after index col) in the DataFrame.. Thanks. – Suraj_j Sep 30 '18 at 10:10
What is your `df.columns`? – hellpanderr Sep 30 '18 at 13:47

score 0 · Answer 2 · answered Sep 27 '18 at 03:50

From this question: Difference between map, applymap and apply methods in Pandas I think what you need is the function apply. It can work on multiple columns. You are using applymap which is oriented for the whole dataframe (but you go around that by selecting a column from your dataframe with df.style)

Here is a toy example:

>>> df = pd.DataFrame([[1,2],[3,4]], columns=['A', 'B'])
>>> df['sum_A_B']=df.apply(lambda x: x['A'] + x['B'], axis=1)
>>> df
   A  B  sum_A_B
0  1  2        3
1  3  4        7

Using Dataframes style.apply for Highlighting based on comparative values

2 Answers2

Linked