A dataset of cracks in photovoltaic backsheets with inner layers of either ethylene-vinyl acetate or polyethylene exposed to 4,000 hours of continuous UVA irradiance with an intensity of 1.55 $w/m^2$ at 340 $nm$ and a chamber temperature of 70$^\circ$C. See the associated journal article in Polymer Degradation and Stability for details on obtaining quantitative crack measurements [@klinke_2018_non-destructive].

130 observations of 5 variables are included:

**Response - dAvgNorm:**average crack depth normalized by the backsheet's inner layer thickness, dimensionless.**Stress - uva360dose:**cumulative, integrated irradiance dose received by the sample for all wavelengths $<$ 360 $nm$, in $MJ/m^2$.**Mechanism - crys730:**percent crystallinity of polyethylene regions determined from the ratio of Fourier transform infrared (FTIR) spectroscopy peak intensities at 731 and 720 $cm^{-1}$ [@huang_attenuated_1992], dimensionless.**Mechanism - carb1715:**ketone carbonyl index determined from the ratio of FTIR peak intensities at 1715 and 2851 $cm^{-1}$, dimensionless.**Mechanism - carbPC1:**1st principal component score for the carbonyl region between 1500 and 1800 $cm^{-1}$.

## Load the crack data set and preview column metadata data(crack) ?crack ## Run netSEM ans <- netSEMm(crack) ## Subset dataset with three cutoffs res <- subsetData(ans, cutoff=c(0.4, 0.5, 0.6)) ## Plot the network model plot(ans, res)

dAvgNorm is the endogenous and all other variables are considered as exagenous.
Based on the plot, the strongest pathway appears to be uva360dose $\rightarrow$ carb1715 $\rightarrow$ dAvgNorm.
This can be confirmed using the `pathwayRMSE()`

function.

knitr::include_graphics("crackplot.png")

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