fakedata_mixsir.m

%This program generates fake data for testing the MixSIR program.
%Written by BX Semmens on 6/30/07

%HOW IT WORKS...
%set isotopes to 2 (this can be easily changed)
%randomly draw the number of sources (2 - 10)
%generate iso sig values for each source (randomize, but constrain to high and low vals for C and N)
%generate SD in sources (randomize, but constrain to high and low values C and N)

%do a random draw to get % contribs for each source


%from that, define the pred iso signature with variance

%DATA:
%mean and variance of sources
%mean and variance of pred

%CREDIBLE INTERVALS FOR TWO ISOTOPES
%CARBON : -35 to -15, SD between 1 and 2
%NITROGEN: 0 to 15, SD between 1 and 2


%CAVIATES
% 1) these simulations are based on the mixture exclusively derived from
% this sources... this assumption is always made in mixing models, but rarely true in
% reality.
%--------------------------------------------------------------------------
clear all;
Cmax=-15;Cmin=-30;CmaxSD=2;CminSD=1;
Nmax=15;Nmin=0;NmaxSD=2;NminSD=1;

%set max number of sources
mxsrc = 5;
%specify the amount of data you want
data_size=50;

%number of sources
src_num = round(rand * (mxsrc-2) + 2); %sets min to two sources, max to mxsrc

%now randomly (uniform over interval) draw iso signatures for each source
for i = 1:src_num
    src_C(i) = rand * (Cmax-Cmin) + Cmin;
    src_Csd(i) = rand * (CmaxSD-CminSD) + CminSD;
    src_N(i) = rand * (Nmax-Nmin) + Nmin;
    src_Nsd(i) = rand * (NmaxSD-NminSD) + NminSD;
    
end

%randomly generate the contribs from each source
contribs = rand_props(src_num);

%now iterate to generate fake mix data
mix = zeros(data_size,2); 
random = randn(data_size,2);
for i=1:data_size
    for j=1:src_num
        mix(i,1)= mix(i,1) + (contribs(j) * (src_C(j)+src_Csd(j).*random(i,1)));
        mix(i,2)= mix(i,2)+ (contribs(j) * (src_N(j)+src_Nsd(j).*random(i,2)));
    end
end

%now write the data files for MixSIR
frac = zeros(src_num,2); %zeros out fractionation
dlmwrite('mean_frac.txt',frac,'\t')
dlmwrite('SD_frac.txt',frac,'\t')
dlmwrite('mix_data.txt',mix,'\t')
%dlmwrite('mean_pred.txt',mean(mix),'\t')
%dlmwrite('SD_pred.txt',std(mix),'\t')
dlmwrite('mean_source.txt',cat(2,src_C',src_N'),'\t')
dlmwrite('SD_source.txt',cat(2,src_Csd',src_Nsd'),'\t')