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What is the base value of Shap?
The base value: The original paper explains that the base value E(y_hat) is “the value that would be predicted if we did not know any features for the current output.” In other words, it is the mean prediction, or mean(yhat). You may wonder why it is 5.62.
What is base value in Shap force plot?
The “base value” (see the grey print towards the upper-left of the image) marks the model’s average prediction over the training set. The “output value” is the model’s prediction: probability 0.64. The feature values for the largest effects are printed at the bottom of the plot.
How do you read Shap values?
How to interpret the shap summary plot?
- The y-axis indicates the variable name, in order of importance from top to bottom. The value next to them is the mean SHAP value.
- On the x-axis is the SHAP value.
- Gradient color indicates the original value for that variable.
- Each point represents a row from the original dataset.
What is Shapley value explain?
The Shapley value is a concept in game theory used to determine contribution of each player in a coalition or a cooperative game. Assume teamwork is needed to finish a project.
What is a negative Shap value?
In this case we can see that for values of RM below 7 (x-axis), the SHAP values (y-axis) are virtually always negative, which means lower values of this feature push the prediction value down. Also, if you have an RM equal to 6, then you can have a SHAP value between -2.5 and 0, depending on the value of RAD.
What is Shap model?
SHAP (SHapley Additive exPlanations) is a game theoretic approach to explain the output of any machine learning model. It connects optimal credit allocation with local explanations using the classic Shapley values from game theory and their related extensions (see papers for details and citations).
What is the base value of Shap tool?
I’ve been trying to understand the SHAP tool and have been puzzled with two terms: base value and the predicted value. The documentation vaguely mentions what the base value is. The documentation says the base value is ‘the average model output over the training dataset we passed’.
How to calculate the Shap value of a variable?
The shap.summary_plot function with plot_type=”bar” let you produce the variable importance plot. A variable importance plot lists the most significant variables in descending order. The top variables contribute more to the model than the bottom ones and thus have high predictive power.
How is a Shapley value interpreted in Shap?
Each individual Shapley value, phi_ij for some feature j and some row x_i, is interpreted as follows: the feature value x_ij contributed phi_ij towards the prediction, yhat_i, for instance x_i compared to the average prediction for the dataset, i.e. mean (yhat).
Which is an example of a Shap model?
One game: one observation. Indeed, SHAP is about local interpretability of a predictive model. By way of example, we will imagine a machine learning model (let’s say a linear regression, but it could be any other machine learning algorithm) that predicts the income of a person knowing age, gender and job of the person.