# BYOM function call_deri.m (calculates the model output)

Syntax: [Xout TE] = call_deri(t,par,X0v)

This function calls the ODE solver to solve the system of differential equations specified in derivatives.m, or the explicit function(s) in simplefun.m. As input, it gets:

*t*the time vector*par*the parameter structure*X0v*a vector with initial states and one concentration (scenario number)

The output *Xout* provides a matrix with time in rows, and states in columns. This function calls derivatives.m. The optional output *TE* is the time at which an event takes place (specified using the events function). The events function is set up to catch discontinuities. It should be specified according to the problem you are simulating. If you want to use parameters that are (or influence) initial states, they have to be included in this function.

- Author: Tjalling Jager
- Date: April 2017
- Web support: http://www.debtox.info/byom.html
- Back to index walkthrough_debkiss_paper.html

## Contents

## Start

```
function [Xout,TE,Xout2] = call_deri(t,par,X0v)
```

global glo % allow for global parameters in structure glo global zvd % global structure for zero-variate data % NOTE: this file is modified so that data and output can be as body length % whereas the state variable remains body weight. Also, there is a % calculation to prevent shrinking in physical length (as shells, for % example, do not shrink).

## Initial settings

This part can be modified by the user to decide whether to calculate the model results using the ODEs in derivatives.m, or the analytical solution in simplefun.m. Further, the events function can be turned on here, initial values can be determined by a parameter, and zero-variate data can be calculated.

useode = glo.useode; % calculate model using ODE solver (1) or analytical solution (0) eventson = glo.eventson; % events function on (1) or off (0) stiff = glo.stiff; % set to 1 to use a stiff solver instead of the standard one % Unpack the vector X0v, which is X0mat for one scenario X0 = X0v(2:end); % these are the intitial states for a scenario % if needed, extract parameters from par that influence initial states in X0 % % start from specified initial size % Lw0 = par.Lw0(1); % initial body length (mm) % X0(2) = glo.dV*((Lw0*glo.delM)^3); % recalculate to dwt, and put this parameter in the correct location of the initial vector % start from the value provided in X0mat if glo.len ~= 0 % only if the switch is set to 1 or 2! % Assume that X0mat includes initial length; if it includes mass, no correction is needed here % The model is set up in masses, so we need to translate the initial length % (in mm body length) to body mass using delM. Assume that size is first state. X0(1) = glo.dV*((X0(1) * glo.delM)^3); % initial length to initial dwt end % % start at hatching, so calculate initial length from egg weight % WB0 = par.WB0(1); % initial dry weight of egg % yVA = par.yVA(1); % yield of structure on assimilates (growth) % kap = par.kap(1); % allocation fraction to soma % WVb = WB0 *yVA * kap; % dry body mass at birth % X0(2) = WVb; % put this estimate in the correct location of the initial vector % % if needed, calculate model values for zero-variate data from parameter set % if ~isempty(zvd) % zvd.ku(3) = par.Piw(1) * par.ke(1); % add model prediction as third value % end

Not enough input arguments. Error in call_deri (line 50) X0 = X0v(2:end); % these are the intitial states for a scenario

## Calculations

This part calls the ODE solver (or the explicit model in simplefun.m) to calculate the output (the value of the state variables over time). There is generally no need to modify this part. The solver ode45 generally works well. For stiff problems, the solver might become very slow; you can try ode15s instead.

c = X0v(1); % the concentration (or scenario number) t = t(:); % force t to be a row vector (needed when useode=0) % specify options for the ODE solver options = odeset; % start with default options if eventson == 1 options = odeset(options, 'Events',@eventsfun); % add an events function end options = odeset(options, 'RelTol',1e-4,'AbsTol',1e-7); % specify tightened tolerances % options = odeset(options,'InitialStep',max(t)/1000,'MaxStep',max(t)/100); % specify smaller stepsize if useode == 1 % use the ODE solver to calculate the solution % call the ODE solver (use ode15s for stiff problems, escpecially for pulses) if isempty(options.Events) % if no events function is specified ... switch stiff case 0 [~,Xout] = ode45(@derivatives,t,X0,options,par,c); case 1 [~,Xout] = ode113(@derivatives,t,X0,options,par,c); case 2 [~,Xout] = ode15s(@derivatives,t,X0,options,par,c); end else % with an events functions ... additional output arguments for events: % TE catches the time of an event, YE the states at the event, and IE the number of the event switch stiff case 0 [~,Xout,TE,YE,IE] = ode45(@derivatives,t,X0,options,par,c); case 1 [~,Xout,TE,YE,IE] = ode113(@derivatives,t,X0,options,par,c); case 2 [~,Xout,TE,YE,IE] = ode15s(@derivatives,t,X0,options,par,c); end end else % alternatively, use an explicit function provided in simplefun! Xout = simplefun(t,X0,par,c); end if isempty(TE) || all(TE == 0) % if there is no event caught TE = +inf; % return infinity end

## Output mapping

*Xout* contains a row for each state variable. It can be mapped to the data. If you need to transform the model values to match the data, do it here.

% here, translate from the state body weight to output in length, if needed if glo.len ~= 0 % only if the switch is set to 1 or 2! % Here, I translate the model output in body mass to estimated physical body length W = Xout(:,1); % Assume that dry body weight is the first state Lw = (W/glo.dV).^(1/3)/glo.delM; % estimated physical body length if glo.len == 2 % when animal cannot shrink in length (but does on volume!) maxLw = 0;%zeros(size(Lw)); % remember max size achieved for i = 1:length(Lw) % run through length data maxLw = max([maxLw;Lw(i)]); % new max is max of old max and previous size Lw(i) = maxLw; % replace value in output vector end end Xout(:,1) = Lw; % replace body weight by physical body length end % % To obtain the output of the derivatives at each time point. The values in % % dXout might be used to replace values in Xout, if the data to be fitted % % are the changes (rates) instead of the state variable itself. % % dXout = zeros(size(Xout)); % initialise with zeros % for i = 1:length(t) % run through all time points % dXout(i,:) = derivatives(t(i),Xout(i,:),par,c); % % derivatives for each stage at each time % end % the part below is highly modified for the specific calculations in the % DEBkiss1 package, to reproduce the figures in the DEBkiss publication if X0v(4) > 0 % there is an initial repro buffer, so we started with a fresh egg! Xout(t>TE,1) = NaN; % don't include body length after point of hatching end % next, calculate respiration from the body length data Lw = Xout(:,1); % shell length from the output matrix (state 1) LV = Lw*glo.delM; % translate to volumetric length JA = par.sJAm(1)*(LV.^2); % embryo assimilation rate for f=1 JA = JA * par.fB(1); % calculate with reduced f for the embryo JM = par.sJM(1)*(LV.^3); % flux for maintenance JV = par.yVA(1)*(par.kap(1)*JA-JM); % flux fixed in structural biomass JD = JA - JV; % dissipation is assimilation minus what is fixed in growth Resp = JD * 130; % proportionality is uL O2/mg dissipated assimilates (see paper) Resp(t<glo.Tlag(1),:) = 0; % during the lag phase, assume no respiration Resp(t>TE,:) = NaN; % don't include respiration after hatching Xout2{1}(:,1) = t; % time is on the x-axis of the extra data set Xout2{1}(:,2) = Resp; % repiration on the y-axis

## Events function

Modify this part of the code if *eventson*=1. This subfunction catches the 'events': in this case, this one catches birth and puberty.

Note that the eventsfun has the same inputs, in the same sequence, as derivatives.m.

function [value,isterminal,direction] = eventsfun(t,X,par,c) WVp = par.WVp(1); % body mass at puberty nevents = 2; % number of events that we try to catch value = zeros(nevents,1); % initialise with zeros value(1) = X(1) - WVp; % thing to follow is body mass (state 1) minus threshold value(2) = X(3); % follow the egg buffer (state 1) to spot hatching isterminal = zeros(nevents,1); % do NOT stop the solver at an event direction = zeros(nevents,1); % catch ALL zero crossing when function is increasing or decreasing