Pandas copy value from another column if condition

Copying values from another column based on a condition using pandas

In pandas, you can copy values from one column to another column based on a certain condition using the `loc` method.

Let’s say we have a dataframe called `df` with two columns – `column1` and `column2`. We want to copy values from `column1` to `column2` if a certain condition is met.

1. First, let’s import the necessary libraries:

<script src="https://cdnjs.cloudflare.com/ajax/libs/pandas/1.1.5/pandas.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

2. Next, create a dataframe `df`:

<script>
    var df = new pandas.DataFrame({
        'column1': [10, 15, 20, 25, 30],
        'column2': [100, 200, 300, 400, 500]
    });
</script>

3. Use the `loc` method to copy values from `column1` to `column2` based on a condition:

<script>
    df.loc[df['column2'] < 300, 'column2'] = df['column1'];
</script>

In this example, we copy the values from `column1` to `column2` only if the value in `column2` is less than 300. The `loc` method allows us to select rows based on conditions and modify specific columns.

4. Finally, print the updated dataframe:

<script>
    console.log(df.to_string());
</script>

By logging the dataframe to the console, you will see the updated values in `column2`:

      column1  column2
    0       10       10
    1       15       15
    2       20       20
    3       25      400
    4       30      500