Curve adjustment is the process of modifying a model's parameters to improve its fit to the data. Validation is the process of evaluating a model's performance on a separate set of data that was not used for training. Validation methods are the techniques used to split the data into training and validation sets, and to measure the model's accuracy, precision, recall, etc.
One common validation method is the **validation curve**, which plots the training and validation scores for different values of a single hyperparameter. This can help you find the optimal value of the hyperparameter that minimizes the bias and variance of the model. You can use the `validation_curve` function from the `sklearn.model_selection` module to generate validation curves for different estimators¹².
Another validation method is the **learning curve**, which plots the training and validation scores for different sizes of the training set. This can help you determine if the model benefits from more training data, or if it suffers from overfitting or underfitting. You can use the `learning_curve` function from the `sklearn.model_selection` module to generate learning curves for different estimators¹.
There are other validation methods, such as cross-validation, bootstrap, hold-out, etc., that you can use depending on your data and model. You can find more information about them in the [User Guide](^1^) and the [Model Validation and Testing: A Step-by-Step Guide](^3^).
Source:
(1) 3.4. Validation curves: plotting scores to evaluate models. https://scikit-learn.org/stable/modules/learning_curve.html.
(2) sklearn.model_selection.validation_curve - scikit-learn. https://scikit-learn.org/stable/modules/generated/sklearn.model_selection.validation_curve.html.
(3) 3.4. Validation curves: plotting scores to evaluate models. https://scikit-learn.org/stable/modules/learning_curve.html.
(4) Model Validation and Testing: A Step-by-Step Guide | Built In. https://builtin.com/data-science/model-validation-test.
(5) Validation Curve - GeeksforGeeks. https://www.geeksforgeeks.org/validation-curve/.
(6) Validation – Adjustment of NIR Calibrations | PerkinElmer Blog. https://blog.perkinelmer.com/posts/validation-adjustment-of-nir-calibrations/.
**Cross-validation** is a method that divides your data into **k** equal and non-overlapping subsets, called **folds**. Then, it trains your model on **k-1** folds, and tests it on the remaining fold. This process is repeated **k** times, so that each fold is used as the test set once. The average of the test scores across the **k** folds is the final performance measure of your model¹.
**Bootstrap** is a method that samples your data **with replacement**, meaning that the same data point can be selected more than once. It creates **B** new datasets, each with the same size as the original dataset, but with some data points repeated and some omitted. Then, it trains your model on each bootstrap dataset, and tests it on the original dataset. The average of the test scores across the **B** bootstrap datasets is the final performance measure of your model².
**Hold-out** is a method that splits your data into two parts: a **training set** and a **validation set**. The training set is used to fit your model, and the validation set is used to evaluate its performance. The size of the validation set is usually a fixed proportion of the original dataset, such as 20% or 30%. The performance measure of your model is the test score on the validation set³.
Each method has its advantages and disadvantages, depending on the size and characteristics of your data, and the complexity and variability of your model. You can find more information about them in the following links:
- [What is the difference between bootstrapping and cross-validation?](^1^)
- [4 Cross Validation Methods | Introduction to Applied Machine Learning](^2^)
- [Hold-out vs. Cross-validation in Machine Learning](^5^)
Source:
(1) What is the difference between bootstrapping and cross-validation?. https://datascience.stackexchange.com/questions/32264/what-is-the-difference-between-bootstrapping-and-cross-validation.
(2) 4 Cross Validation Methods | Introduction to Applied Machine Learning. https://dionysus.psych.wisc.edu/iaml_2020/unit-04.html.
(3) Are K-Fold Cross Validation , Bootstrap ,Out of Bag fundamentally same?. https://stats.stackexchange.com/questions/206807/are-k-fold-cross-validation-bootstrap-out-of-bag-fundamentally-same.
(4) What is the difference between bootstrapping and cross-validation?. https://datascience.stackexchange.com/questions/32264/what-is-the-difference-between-bootstrapping-and-cross-validation.
(5) 4 Cross Validation Methods | Introduction to Applied Machine Learning. https://dionysus.psych.wisc.edu/iaml_2020/unit-04.html.
(6) Hold-out vs. Cross-validation in Machine Learning - Medium. https://medium.com/@jaz1/holdout-vs-cross-validation-in-machine-learning-7637112d3f8f.
(7) Bootstrapping vs Cross-Validation - Doc Zamora's ML & AI. https://www.doczamora.com/bootstrapping-vs-cross-validation.
(8) en.wikipedia.org. https://en.wikipedia.org/wiki/Cross-validation_(statistics).
How do I choose the best validation method for my model?
Choosing the best validation method for your model depends on several factors, such as the size and characteristics of your data, the complexity and variability of your model, and the trade-off between bias and variance. 😊
There is no definitive answer to this question, as different validation methods have their own advantages and disadvantages. However, some general guidelines are:
- If your data is large and representative, you can use a simple **hold-out** method, where you split your data into a training set and a validation set, and use the validation set to evaluate your model's performance⁴.
- If your data is small or imbalanced, you can use a **cross-validation** method, where you divide your data into k folds, and use each fold as a validation set once, while using the rest as a training set. This way, you can use all your data for both training and validation, and reduce the variance of your model's performance¹.
- If your data is noisy or has high variance, you can use a **bootstrap** method, where you sample your data with replacement, and create new datasets that have the same size as the original dataset. Then, you can train and test your model on each bootstrap dataset, and average the performance across them. This way, you can reduce the bias of your model's performance².
You can also combine different validation methods, such as using cross-validation with hold-out, or bootstrap with cross-validation, to get more robust estimates of your model's performance.
To learn more about these validation methods, you can check out these links:
- [Model Validation and Testing: A Step-by-Step Guide](^1^)
- [The Ultimate Guide to Evaluation and Selection of Models in ML](^2^)
- [choosing model based on last or best iteration on validation set](^3^)
- [How To Choose The Right Test Options When Evaluating Machine Learning Algorithms](^4^)
Source:
(1) How To Choose The Right Test Options When Evaluating Machine Learning .... https://machinelearningmastery.com/how-to-choose-the-right-test-options-when-evaluating-machine-learning-algorithms/.
(2) Model Validation and Testing: A Step-by-Step Guide | Built In. https://builtin.com/data-science/model-validation-test.
(3) The Ultimate Guide to Evaluation and Selection of Models in ML - neptune.ai. https://neptune.ai/blog/ml-model-evaluation-and-selection.
(4) Model Validation and Testing: A Step-by-Step Guide | Built In. https://builtin.com/data-science/model-validation-test.
(5) The Ultimate Guide to Evaluation and Selection of Models in ML - neptune.ai. https://neptune.ai/blog/ml-model-evaluation-and-selection.
(6) choosing model based on last or best iteration on validation set. https://datascience.stackexchange.com/questions/72002/choosing-model-based-on-last-or-best-iteration-on-validation-set.
(7) How To Choose The Right Test Options When Evaluating Machine Learning .... https://machinelearningmastery.com/how-to-choose-the-right-test-options-when-evaluating-machine-learning-algorithms/.
How do I measure the performance of my model?
There are different ways to measure the performance of your model, depending on the type of problem you are solving and the metrics you are interested in. 😊
For example, if you are solving a **classification** problem, where you want to predict discrete labels for your data, you can use metrics such as **accuracy**, **precision**, **recall**, and **F1 score**. These metrics evaluate how well your model can correctly identify the true classes of your data, and avoid false positives and false negatives. You can also use plots such as **ROC curve** and **confusion matrix** to visualize the trade-off between sensitivity and specificity, and the distribution of errors across classes¹².
If you are solving a **regression** problem, where you want to predict continuous values for your data, you can use metrics such as **mean absolute error (MAE)**, **root mean square error (RMSE)**, **R-squared**, and **adjusted R-squared**. These metrics evaluate how close your model's predictions are to the true values of your data, and how well your model can explain the variance of your data. You can also use plots such as **residual plot** and **scatter plot** to visualize the error distribution and the correlation between your predictions and true values³⁴.
To learn more about these metrics and plots, and how to implement them in Python, you can check out these links:
- [Evaluate the Performance of Deep Learning Models in Keras](^1^)
- [6 Methods to Measure Performance of a Classification Model](^2^)
- [4 Best Metrics for Evaluating Regression Model Performance](^3^)
- [Predictive Performance Models Evaluation Metrics](^5^)
Source:
(1) Evaluate the Performance of Deep Learning Models in Keras. https://machinelearningmastery.com/evaluate-performance-deep-learning-models-keras/.
(2) 6 Methods to Measure Performance of a Classification Model. https://insidelearningmachines.com/measure-performance-of-a-classification-model/.
(3) Evaluate Models Using Metrics | Machine Learning - Google Developers. https://developers.google.com/machine-learning/testing-debugging/metrics/metrics.
(4) 4 Best Metrics for Evaluating Regression Model Performance. https://www.aionlinecourse.com/tutorial/machine-learning/evaluating-regression-models-performance.
(5) Evaluate the Performance of Deep Learning Models in Keras. https://machinelearningmastery.com/evaluate-performance-deep-learning-models-keras/.
(6) 6 Methods to Measure Performance of a Classification Model. https://insidelearningmachines.com/measure-performance-of-a-classification-model/.
(7) Evaluate Models Using Metrics | Machine Learning - Google Developers. https://developers.google.com/machine-learning/testing-debugging/metrics/metrics.
(8) Predictive Performance Models Evaluation Metrics - InData Labs. https://indatalabs.com/blog/predictive-models-performance-evaluation-important.
(9) en.wikipedia.org. https://en.wikipedia.org/wiki/Keras.
What is the difference between accuracy and precision?
Accuracy and precision are both forms of measurement that define how close you are to hitting a target or achieving a goal. Accuracy evaluates how close you are to the true value of the measurement, while precision shows how close the measured values are to one another¹.
For example, if you are shooting arrows at a bullseye, accuracy is how close your arrows are to the center of the target, and precision is how close your arrows are to each other. You can have high accuracy and low precision, low accuracy and high precision, or both high accuracy and high precision².
In math, science, and engineering, accuracy and precision are used to describe the quality and reliability of measurements. Accuracy reflects how close a measurement is to the actual or accepted value, while precision reflects how consistent or reproducible the measurements are. A measurement system can be accurate but not precise, precise but not accurate, or both accurate and precise³.
Source:
(1) What Is the Difference Between Accuracy and Precision? - ThoughtCo. https://www.thoughtco.com/difference-between-accuracy-and-precision-609328.
(2) Accuracy and precision - Wikipedia. https://en.wikipedia.org/wiki/Accuracy_and_precision.
(3) What's the difference between accuracy and precision? - Asana. https://asana.com/resources/accuracy-vs-precision.
(4) What Is the Difference Between Accuracy and Precision? - ThoughtCo. https://www.thoughtco.com/difference-between-accuracy-and-precision-609328.
(5) Accuracy and precision - Wikipedia. https://en.wikipedia.org/wiki/Accuracy_and_precision.
(6) What's the difference between accuracy and precision? - Asana. https://asana.com/resources/accuracy-vs-precision.
How do I calculate accuracy and precision for my model?
Accuracy and precision are two metrics that can be used to evaluate the performance of a classification model. Accuracy is the ratio of the number of correct predictions to the total number of predictions, while precision is the ratio of the number of true positives to the total number of positive predictions¹.
To calculate accuracy and precision for your model, you need to have the true labels and the predicted labels of your data. You can use the `sklearn.metrics` module in Python to compute these metrics easily. For example, you can use the following code:
```python
from sklearn.metrics import accuracy_score, precision_score
# y_true is the list of true labels
# y_pred is the list of predicted labels
accuracy = accuracy_score(y_true, y_pred)
precision = precision_score(y_true, y_pred)
print("Accuracy:", accuracy)
print("Precision:", precision)
```
You can also use other metrics, such as recall, F1-score, ROC AUC, etc., depending on your problem and goals. You can find more information about these metrics and how to calculate them in the following links:
- [How to Calculate Precision, Recall, F1, and More for Deep Learning Models](^1^)
- [How to Calculate Precision, Recall, and F-Measure for Imbalanced Classification](^2^)
- [Model accuracy: how to determine it? - Data Science Stack Exchange](^4^)
Source:
(1) How to Calculate Precision, Recall, F1, and More for Deep Learning Models. https://machinelearningmastery.com/how-to-calculate-precision-recall-f1-and-more-for-deep-learning-models/.
(2) How to Calculate Precision, Recall, F1, and More for Deep Learning Models. https://machinelearningmastery.com/how-to-calculate-precision-recall-f1-and-more-for-deep-learning-models/.
(3) How to Calculate Precision, Recall, and F-Measure for Imbalanced .... https://machinelearningmastery.com/precision-recall-and-f-measure-for-imbalanced-classification/.
(4) Model accuracy: how to determine it? - Data Science Stack Exchange. https://datascience.stackexchange.com/questions/83961/model-accuracy-how-to-determine-it.
(5) How to Calculate Accuracy and Precision: A Comprehensive Guide. https://www.thetechedvocate.org/how-to-calculate-accuracy-and-precision-a-comprehensive-guide/.
(6) How Compute Accuracy For Object Detection works - Esri. https://pro.arcgis.com/en/pro-app/latest/tool-reference/image-analyst/how-compute-accuracy-for-object-detection-works.htm.
