ode15s integrating over arbitrary function

Hi there,

Im trying to solve this very simple differential equation.

y(t)'=r(T(t))

where r is a rate curve (development as a function of temperature) and T is an arbitrary Temperature profile. I am trying to solve this but i get this error.

%-------------------------------------------------------%
  Error using griddedInterpolant
  The grid vectors are not strictly monotonic increasing.

    Error in interp1 (line 191)
            F = griddedInterpolant(X,V,method);

    Error in test_ode_mass>Mass (line 97)
        M=interp1(x(1,:),x(2,:),t);

    Error in test_ode_mass>oderatecurveVar (line 90)
        dy(1)=Mass(t,x);

    Error in odearguments (line 88)
    f0 = feval(ode,t0,y0,args{:});   % ODE15I sets args{1} to yp0.

    Error in ode15s (line 149)
    [neq, tspan, ntspan, next, t0, tfinal, tdir, y0, f0, odeArgs, odeFcn, ...

    Error in test_ode_mass (line 59)
               [a cumulativeDevelopment(i,:)] = ode15s(@oderatecurveVar,t,ynot(i), odeset('RelTol',1e-10),
               [rT(i,:); t]);

%-------------------------------------------------------%

I have attached to code to the bottom. The main goal is to find a way to solve the differential equation for an arbitrary Temperature profile only specified by a set of data points (not a function). ie a vector of data points relating temperature to time.

%-------------------------------------------------------%

    %test new ode solving method
    function test_ode_mass
        clear all
        format long

        %============================================================================ %

            % time in days
            td=.05;
            tend=365;
            t=0:td:tend;  

            % temperature variations     
            T0=10;  %average yearly temperature
            T1=13;  %average fluxuation in temperature per year
            Tf=0;   %average fluxuation in temperature per day
            tPerturb=0;      % perturb the temprature by this amount;

            % % temperature variations     
                % T0=5; %average yearly temperature
                % T1=15; %average fluxuation in temperature per year
                % Tf=8; %average fluxuation in temperature per day
                % tPerturb=0;      % perturb the temprature by this amount;

            % temperature spike variables
            pertTempAmp=10;
            pertTempExpTime=50;
            pertTempDev=0.7;
            pertTemperatur=pertTempAmp*exp(-(((t-pertTempExpTime)/pertTempDev).^2)/2);

             % perturb the temprature by this amount;
            tPhaseShift=pi;  % this parameter has no effect on the Gfunction2
            tPhaseShift=round(tPhaseShift*10^7)/10^7;

            % Temperature spike

            T=(T0-T1*cos(2*pi*t/365-tPhaseShift)+(Tf)*cos(pi*t*2)+tPerturb+pertTemperatur);

            %TEMPERATURE PLOT
            figure
                % subplot(3,1,1)
                plot(t,T)
                title('Temperature as a function of time')
                xlabel('Time (days)')
                ylabel('Temperature (K)')
                axis([min(t) 365 min(T) max(T)])

            xr(1,:)={67,8,1.6,1.7,20, T};
            xr(2,:)={100,7,1.4,1.8,20.0,T};
            xr(3,:)={66,5.5,2,0.4,2.4,T};    
            xr(4,:)={3,3.5,2.5,0.5,3.5,T};     

            ynot=zeros(1,length(xr(:,1)));
            % options=odeset('RelTol',1e-6,'Stats','on')
            for i=1:length(xr(:,1))
              rT(i,:)=findRateCurveVar(xr(i,:),t);
               [a cumulativeDevelopment(i,:)] = ode15s(@oderatecurveVar,t,ynot(i), odeset('RelTol',1e-10), [rT(i,:); t]);
            end

    end
    %--------------------------------------------%

    function rT=findRateCurveVar(x,t)
        %%Find Theoretical Developmental rate curves YURK POWELL 2009
        %
        %   Assume that the funcitonal form is
        %
        %   a;  maximum developmental time
        %   b;  changes the width of the deveoplental times
        %   c;  slop at lower tempeature threshold
        %   d;  slope at higher threshold temp
        %   theta;  Optimal gorwing temperature (@ minimum develpmental time)
        a=x{1};
        b=x{2};
        c=x{3};
        d=x{4};
        theta = x{5};
        T=x{6};

        rT=(1./(a+exp(b-theta*(d+c)+d.*(T)))).*heaviside(T-theta)+(1./(a+exp(b-c.*(T)))).*heaviside(theta-T);

    end

    %--------------------------------------------%

    function dy = oderatecurveVar(t,y,x)
        dy=zeros(1,1);
        dy(1)=Mass(t,x);

    end

    %--------------------------------------------%

    function M=Mass(t,x)
        M=interp1(x(1,:),x(2,:),t);

    end