# Generate a starting value for N Generate a starting value for `N`, which represents the number of individuals in each length class for each species. ```r get_N0(nsc, nfish, mid, wgt, sc_Linf, intercept = 1e+10, slope = -5) ``` ## Arguments - `nsc`: A numeric value representing the number of length classes in the model. - `nfish`: A numeric value representing the number of fish species in the model. - `mid`: A numeric vector of length `nfish` representing the mid-point of the length classes. - `wgt`: A matrix with dimensions `nsc` and `nfish` representing the weight of each species in each length class. - `sc_Linf`: A numeric vector of length `nsc` representing the length class at which each species reaches its asymptotic length. - `intercept`: A numeric value representing the number of individuals in the first length class. The default is `1e10`. - `slope`: A numeric value representing the slope of the community size spectrum. The default is -5. ## Returns A matrix with dimensions `nsc` and `nfish` representing the number of individuals in each length class. ## Details The total number of individuals in the community in each length class is equal to `intercept*mid^slope`. Within each length class, the number of individuals of each species is determined using the proportion of each species' biomass that is found in that length class. ## Examples ```r # Set up the inputs to the function nfish <- nrow(NS_par) nsc <- 32 maxsize <- max(NS_par$Linf)*1.01 # the biggest size is 1% bigger than the largest Linf l_bound <- seq(0, maxsize, maxsize/nsc); l_bound <- l_bound[-length(l_bound)] u_bound <- seq(maxsize/nsc, maxsize, maxsize/nsc) mid <- l_bound+(u_bound-l_bound)/2 # Set up the inputs to the function - species-specific parameters Linf <- NS_par$Linf # the von-Bertalanffy asymptotic length of each species (cm). W_a <- NS_par$W_a # length-weight conversion parameter. W_b <- NS_par$W_b # length-weight conversion parameter. k <- NS_par$k # the von-Bertalnaffy growth parameter. Lmat <- NS_par$Lmat # the length at which 50\% of individuals are mature (cm). # Get phi_min tmp <- calc_phi(k, Linf, nsc, nfish, u_bound, l_bound, calc_phi_min=FALSE, phi_min=0.1) # fixed phi_min phi_min <- tmp$phi_min # Calculate growth increments tmp <- calc_ration_growthfac(k, Linf, nsc, nfish, l_bound, u_bound, mid, W_a, W_b, phi_min) sc_Linf <- tmp$sc_Linf wgt <- tmp$wgt # Get an initial population get_N0(nsc, nfish, mid, wgt, sc_Linf) ``` ## References Andersen, K.H., Blanchard, J.L., Fulton, E.A., Gislason, H., Jacobsen, N.S., van Kooten, T. (2016). Assumptions behind size-based ecosystem models are realistic. **ICES Journal of Marine Science**, 73(6):1651-1655. ## See Also `run_LeMans`

get_N0 function