Develop an R function to draw a density curve representing the probability density function of a continuous variable, with separate curves for each group , using ggplot2.

The document provides a detailed description of the data sources and methods used for population attribution of noise exposure in Stockholm County, as applied in the BMHE2019 and MHpK2024 projects. It outlines the methodology for estimating the number of people exposed to road traffic, railway, and aircraft noise above 55 dB, using 2019 population data stratified by age groups and administrative classifications. The analysis incorporates data from SCB, Trafikverket, Trafikförvaltningen, and Swedavia, along with GIS-based spatial assessments.

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