TypeError: unsupported operand type(s) for -: 'float' and 'str'

Question

I am new to Python and am stuck with what to do right now because I keep getting this error.I am trying to change the following equation like:

z = np.power(((float(X) * theta.T)-float(Y)), 2)

but I can't seem to get it to work.

My code:

# convert from data frames to numpy matrices
X = np.matrix(x.values)  
Y = np.matrix(y.values)  
theta = np.matrix(np.array([0,0]))
# cost functionstrong text
def computeCost(X, Y, theta):
    z = np.power(((X * theta.T)-Y), 2)
    return np.sum(z) / (2 * len(X))
print('computeCost(X, y, theta) = ' , computeCost(X, Y, theta))

the matrix is full of float numbers:

 X = [[ 1.      6.1101] [ 1.      5.5277] [ 1.      8.5186] ...

The error message:

TypeError: unsupported operand type(s) for -: 'float' and 'str'

I appreciate all the help I can get. Thanks a lot

Answer 1

do check datatypes of your dataframe

df.info()

if there's 'object' datatype, that's your string

you may want all datatypes in your dataframe as float, you can do it

df.astype('float')