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I looked for this error on stackoverflow and found several posts, but no one adressing this specific situation.
I have the following dataframe:
the inputvariables and outputvariables are defined in this code:
xcol=["h","o","p","d","ddlt","devdlt","sl","lt"]
ycol=["Q","r"]
x=df[xcol].values
y=df[ycol].values
My goal is to guess the output values Q & r, based on the inputs (x).
I have tried two ways and both are failing. With the first one, I tried a multi-ouput regressor.
I first split up the data in test and training data:
import numpy as np
from sklearn.model_selection import train_test_split
X_train, X_test, y_train, y_test = train_test_split(x, y, test_size=0.2)
y_train = y_train.ravel()
y_test = y_test.ravel()
then import the function:
from sklearn.multioutput import MultiOutputRegressor
and then try to predict Q & r:
reg= MultiOutputRegressor(estimator=100, n_jobs=None)
reg=reg.predict(X_train, y_train)
And this gives me the error:
TypeError: predict() takes 2 positional arguments but 3 were given
What am I doing wrong and how can I fix it?
Next thing I tried was a neural network. After assigning the columns x and y, I made the neural network:
# neural network class definition
class neuralNetwork:
#Step 1:
def __init__(self, inputnodes, hiddennodes, outputnodes, learningrate):
#set number of nodes in each input, hidden, output layer
self.inodes = inputnodes
self.hnodes = hiddennodes
self.onodes = outputnodes
#link weight matrices, wih and who (weights in hidden en output layers),
# we are going to create matrices for the multiplication of it to get an
# output
# weights inside the arrays (matrices) are w_i_j, where link is from node
# i to node j in the next layer
#w11 w21
#w12 w22 etc
self.wih = numpy.random.normal(0.0,pow(self.inodes,-0.5),( self.hnodes,
self.inodes))
self.who = numpy.random.normal(0.0,pow(self.hnodes,-0.5),( self.onodes,
self.hnodes))
# setting the learning rate
self.lr = learningrate
# activation function is the sigmoid function
self.activation_function = lambda x: scipy.special.expit(x)
#Step 2:
def train(self, inputs_list, targets_list):
#convert input lists to 2d array (matrice)
inputs = numpy.array(inputs_list, ndmin=2).T
targets = numpy.array(targets_list, ndmin=2).T
#calculate signals into hidden layer
hidden_inputs = numpy.dot(self.wih, inputs)
#calculate signals emerging from hidden layer
hidden_outputs = self.activation_function(hidden_inputs)
#calculate signals into final output layer
final_inputs = numpy.dot(self.who, hidden_outputs)
#calculate signals emerging from final output layer
final_outputs = self.activation_function(final_inputs)
# output layer error is the (target-actual)
output_errors = targets -final_outputs
#hidden layer error is the output_errors, split by weights, recombined
at hidden nodes
hidden_errors = numpy.dot(self.who.T, output_errors)
#update the weights for the links between the hidden and output layers
self.who += self.lr * numpy.dot((output_errors*final_outputs * (1.0-
final_outputs)),numpy.transpose(hidden_outputs))
# update the weights for the links between the input and hidden layers
self.wih += self.lr*numpy.dot((hidden_errors*hidden_outputs*(1.0-
hidden_outputs)),numpy.transpose(inputs))
#Step 3
def query(self, inputs_list):
#convert input lists to 2d array (matrice)
inputs = numpy.array(inputs_list, ndmin=2).T
#calculate signals into hidden layer
hidden_inputs = numpy.dot(self.wih, inputs)
#calculate signals emerging from hidden layer
hidden_outputs = self.activation_function(hidden_inputs)
#calculate signals into final output layer
final_inputs = numpy.dot(self.who, hidden_outputs)
#calculate signals emerging from final output layer
final_outputs = self.activation_function(final_inputs)
return final_outputs
I then created an instance of a neural network:
#Creating instance of neural network
#number of input, hidden and output nodes
input_nodes = 8
hidden_nodes = 100
output_nodes = 2
#learning rate is 0.8
learning_rate = 0.8
#create instance of neural network
n = neuralNetwork(input_nodes, hidden_nodes, output_nodes, learning_rate)
I got 8 inputs and 2 outputs that need to be predicted.
I then trained the neural network:
# train the neural network
# go through all records in the training data set
for record in df:
#scale and shift te inputs
inputs = x
#create the target output values
targets = y
n.train(inputs, targets)
and then I want to query the guessed outputs and now it goes wrong:
so i want to make 2 extra columns in the dataframe with the guesses of Q (Q*) & r (r*):
df["Q*","r*"] = n.query(x)
I really don't know how to do this properly. This above code gives me the error:
ValueError: Length of values does not match length of index
Any help appreciated.
Steven
Regarding the first part (MultiOutputRegressor) of your question, there are several issues with your code...
To start with, the estimator argument of MultiOutputRegressor should not be a number, but, as the docs say:
estimator : estimator object
An estimator object implementing fit and predict.
So, for example, to use a random forest with default parameters, you should use
reg = MultiOutputRegressor(RandomForestRegressor())
(see this answer for some more examples)
Second, in your code you never fit your regressor; you should add
reg.fit(X_train, y_train)
after the definition.
Third, predict doesn't take the ground truth values (y_train here) as arguments, only the features (X_train); from the docs again:
predict(X)
Predict multi-output variable using a model
trained for each target variable.
Parameters: X : (sparse) array-like, shape (n_samples, n_features)
Data.
Returns: y : (sparse) array-like, shape (n_samples, n_outputs)
Multi-output targets predicted across multiple predictors. Note: Separate models are generated for each predictor.
Since you also pass y_train in your code, you receive an expected error of one argument too many; simply change it to reg.predict(X_train), and you will be fine.
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