California Housing Price Predictor

Predicts the median house value of a California census district (block group, 1990 census) from 8 features: median income, house age, rooms, bedrooms, population, occupancy, latitude and longitude. The default model is XGBoost, and a PyTorch MLP is included as an alternative. Both were trained on sklearn's California Housing dataset. On the held-out test split (4,128 districts), XGBoost reaches R² 0.853 with an RMSE of $43,966 and an MAE of $28,540 (retrained 2026-09-25, metrics.json).

Model

• Input: one district as a dict with the 8 raw features MedInc (median income in $10k), HouseAge, AveRooms, AveBedrms, Population, AveOccup, Latitude, Longitude (same units as sklearn).
• Features (model.engineer): the 8 raw features plus 3 ratios from the classic recipe: rooms_per_household, bedrooms_per_room = AveBedrms / AveRooms and population_per_household. sklearn's version is already per household, so the first and last ratio equal AveRooms and AveOccup. They are kept to mirror the recipe; bedrooms_per_room is the only new signal. This gives 11 columns, in the order stored in config.json["features"].
• xgboost (default, xgb.ubj): XGBRegressor with hist trees, depth 6, learning rate 0.05, subsample and column subsample 0.8. Early stopping on validation RMSE picked round 1,085 of at most 2,000, and the booster is saved trimmed to those 1,085 trees in XGBoost's native format. It uses the unscaled features.
• mlp (alternative, model.safetensors + config.json): HousingMLP, a PyTorchModelHubMixin module 11-256-128-64-1 with ReLU and dropout 0.15 (44,289 parameters). Its inputs are standardized by scaler.joblib, a StandardScaler fit on the train split.
• Output: predict(features, model="best") returns {"price_usd": 368791.17, "model": "xgboost"}. The model predicts MedHouseVal in $100k; the value is floored at 0 and multiplied by 100,000. model can be "best", "xgboost" or "mlp".
• config.json holds the MLP's init arguments (read back by HousingMLP.from_pretrained), the feature order and formulas, the default model, each model's validation RMSE and the library versions.

Usage

from huggingface_hub import snapshot_download
import sys
path = snapshot_download("shalev396/california-housing")
sys.path.insert(0, path)
import model
predictor = model.load(path, device="cpu")   # the MLP can also run on "cuda"; XGBoost always runs on the CPU
print(predictor.predict({"MedInc": 4.445, "HouseAge": 52, "AveRooms": 5.5346, "AveBedrms": 1.1509,
                         "Population": 742, "AveOccup": 2.3333, "Latitude": 37.77, "Longitude": -122.43}))
# {'price_usd': 368791.17, 'model': 'xgboost'}   (actual value of this San Francisco district: $400,000)

• Space API: the Space serves the same code at POST /gradio_api/call/predict (8 numbers + model name -> [result, seconds, device]).
• Inference Endpoint: handler.py makes this repo deployable as a custom Inference Endpoint. Request {"inputs": {<8 features>}, "parameters": {"model": "best"}}; a list of districts returns a list of results.

Training

• Data: 20,640 California block groups from the 1990 US census (StatLib), loaded with sklearn.datasets.fetch_california_housing. The target MedHouseVal is capped at 5.00001 ($500,001) in the source data.
• Split: 80/20 train/test with seed 42, then 15 % of the train part as validation: 14,035 / 2,477 / 4,128 districts.
• Experiments: LinearRegression, RandomForest (200 trees), XGBoost (early stopping, 50 rounds patience) and the MLP (AdamW lr 1e-3, weight decay 1e-4, batch 256, MSE loss, early stopping with patience 10: best epoch 81 of 91). All are fit on the train split.
• Selection: the default model is the exported model with the lowest validation RMSE. The test split is scored once, after that choice.
• Hardware / time: CPU only. The run was measured on a shared 20-thread desktop CPU that several other training jobs were using at the same time (6 threads for this run), so its fit times are much slower than an idle machine would give: XGBoost 1,205 s, MLP 956 s, RandomForest 8 s.
• Full code: training/ · Colab

Evaluation

Default model (XGBoost) on the test split. RMSE and MAE are in $100k (the target unit); the _usd rows are in dollars:

Experiments

Every experiment, ranked by validation RMSE. The default model is in bold:

XGBoost wins: it beats the MLP and the RandomForest by $7-8k of test RMSE. The earlier version of this project reported almost the same XGBoost result (test RMSE 0.4423, R² 0.851) with the same split and XGBoost settings.

Median income carries 42 % of XGBoost's total gain; location (longitude + latitude) carries another 25 %.

Limitations

• 1990 data: prices are 1990 district medians in 1990 dollars. They say nothing about today's market or about a single house.
• Capped target: the source data caps values at $500,001, so the model never learned what lies above it. Capped districts are often underestimated (the vertical column at $500k in the scatter plot), and predictions rarely go past about $540k.
• District-level features: the inputs are averages over a block group (hundreds to thousands of people), not properties of one home.
• Extrapolation: inputs far outside the training ranges (for example coordinates outside California) still return a number, but it is meaningless.
• Duplicate ratios: two of the three engineered features duplicate raw columns (see Model). This is harmless for the trees and the scaled MLP, but they add no information.