#use ordinal encoder to encode experience level
encoder = OrdinalEncoder(categories=[['EN', 'MI', 'SE', 'EX']])
salary_data['experience_level_encoded'] = encoder.fit_transform(salary_data[['experience_level']])

#use ordinal encoder to encode company size
encoder = OrdinalEncoder(categories=[['S', 'M', 'L']])
salary_data['company_size_encoded'] = encoder.fit_transform(salary_data[['company_size']])

#encode employmeny type and job title using dummy columns
salary_data = pd.get_dummies(salary_data, columns = ['employment_type', 'job_title'], drop_first = True, dtype = int)

#drop original columns
salary_data = salary_data.drop(columns = ['experience_level', 'company_size'])