How to update column x at row where column y = z[QUESTION]

[gagecarto]

Ask your question I am having a hard time figuring out how to update a particular cell value by first selecting a row.

Let's say I have a dataframe with columns x,y & z

I'd like to update column x to a value of 999 at the row where column y == 5

I know I can select the appropriate row by doing df.filter(row => row.get('y') === 5)

I tried chaining this to a set call but was obviously first subsetting the entire dataframe.

df= df.chain( row => row.get('y') == 5, // filter row => row.set('x', 999) // map )

Any suggestions?

Additional context Add any other context or screenshots about the question here.

[gagecarto]

I was able to figure this out using a combination of prerolled row indices and set row function.. It worked like this

rowIndices=myDf.toDict()['y']

function updateDf(rowValue,newValue){
  var tempIndex=rowIndices.indexOf(rowValue)
  myDf=myDf.setRow(tempIndex, row => row.set('x',999))
}

// i can now update column x to 999 where row y == 5 using function call like below
updateDf(5,999)