Axis Equals One Syntax Error

I want to make a a step function plot using values from a txt file to run equations that will generate a plot. My txt file looks something like x0 x1 y0 y1

Solution 1:

You have missed a matching brace there after "+row.y0 " . It should be "+row.y0)":

df['u'] = df.apply(lambda row: (((row.y1-row.y0)/(row.x1-row.x0)*(1-row.x0))+row.y0 ) , axis=1)

This must fix that syntax error