Thread: Matlab looping/plotting problem

Hey all,

I have a script written to predict elevation in two loops. One ("small loop") calculates elevation over fifty timesteps, and creates records of all the necessary data (elevation, etc.). The second ("large loop") contains the small loop, runs twenty times, and plots the records after each set of 50 iterations of the small loop. The large loop wipes the records clean at the beginning of each of its 20 iterations, and creates new, empty records and defines all the relavent variables before the small loop starts.

The script works fine, I get 20 unique elevation records of 50 timesteps each, but the plot only ever records two records at a time, and then it wipes itself clean and plots the next two, before wiping itself clean again (i.e. it plots iterations 1 and 2 of the large loop, then iterations 3 and 4, 5 and 6, and so on, but never more than two at once). I've checked my hold on command, and it seems to be placed properly -- I have one at the end of the plotting commands, which are in the large loop, but after the small loop.

So basically I need to figure out why it won't plot more than two lines at once, and then to figure out how to plot all twenty lines on the same plot.

Help would be appreciated!

Thanks in advance,

-Brad

Originally Posted by bp023

Hey all,

I have a script written to predict elevation in two loops. One ("small loop") calculates elevation over fifty timesteps, and creates records of all the necessary data (elevation, etc.). The second ("large loop") contains the small loop, runs twenty times, and plots the records after each set of 50 iterations of the small loop. The large loop wipes the records clean at the beginning of each of its 20 iterations, and creates new, empty records and defines all the relavent variables before the small loop starts.

The script works fine, I get 20 unique elevation records of 50 timesteps each, but the plot only ever records two records at a time, and then it wipes itself clean and plots the next two, before wiping itself clean again (i.e. it plots iterations 1 and 2 of the large loop, then iterations 3 and 4, 5 and 6, and so on, but never more than two at once). I've checked my hold on command, and it seems to be placed properly -- I have one at the end of the plotting commands, which are in the large loop, but after the small loop.

So basically I need to figure out why it won't plot more than two lines at once, and then to figure out how to plot all twenty lines on the same plot.

Help would be appreciated!

Thanks in advance,

-Brad

Can we see the code?

CB

Sure -- the calls to other scripts (i.e. volume, elev_area) are just functions written in other files. And sorry in advance that all the justification is thrown off.




% MONONEW - script to predict the water level in Lake Mono, CA
% Updated 21 February by Brad Peters

clear %clear existing workspace variables



%define timespace variables

time_max = 10; %total time for simulation (yrs)
dt = 1; %simulation time interval (yrs)

%set imax

jmax = time_max/dt; %sets the maximum number of iterations for the model

for j = 1:jmax

clear %clear existing workspace variables

%statistical data for inputs
mu_q_in = 167.47;
sigma_q_in = 53.19;
mu_p = 0.66;
sigma_p = 0.25;
mu_e = 3.58;
sigma_e = 0.26;

% initial parameters

r = randn(50,1); %random number generation from a (0,1) std nml distrib
e0 = 6374; %initial elev (ft)
v0 = volume(e0); %initial volume calculation (1000 acre - ft)
a0 = elev_area(e0); %initial area calculation (1000 acres)

%create datasets from initial parameters

volume_mono = [v0]; %creates variable volume_mono, starting with v0 (1000 acre-ft)
area_mono = [a0]; %creates variable area_mono, starting with a0 (1000 acres)
elev_mono = [e0]; %creates variable elev_mono, starting wtih e0 (ft)

%create empty record datasets

volume_record = []; %creates empty record dataset for volume
area_record = []; %creates empty record dataset for area
elev_record = []; %creates empty record dataset for elevation
q_record = []; %creates empty record dataset for overland flows
p_record = []; %creates empty record dataset for precipitation
e_record = []; %creates empty record dataset for evaporation
d_record = []; %creates empty record dataset for diversions
e_t_record = []; %creates empty record dataset for target elevation

%clear figure

figure(1) %calls figure 1

%define timespace variables

time_max_new = 50; %total time for simulation (yrs)
dt_new = 1; %simulation time interval (yrs)

%set imax

imax_new = time_max_new/dt_new; %sets the maximum number of iterations for the model

for i = 1:imax_new %starts calculation loop for i=1 through i=imax

time = i*dt_new; %defines variable "time"

%make datasets from excel calls or random number grabs

q = (r(i,1)*sigma_q_in)+mu_q_in; %calculates overland flow levels from random number grab
p_r = (r(i,1)*sigma_p)+mu_p; %calculates precipitation levels from random number grab
e_r = -((r(i,1)*sigma_e)+mu_e); %calculates evaporation levels from random number grab
e_t = 6392; %defines target elevation

%function calls

area_mono = area(volume_mono); %calculates lake area given lake volume
elev_mono = elevation(volume_mono); %calculates lake elevation given lake volume

%volume of evap/precip

v_p = p_r*area_mono; %calculates volume of precipitation given height of precipitation (1000 ac-ft/yr)
v_e = e_r*area_mono; %calculates volume of evaporation given height of evaporation (1000 ac-ft/yr)

%calculation loop

if elev_mono >= 6380 %calculation only for given elevation range
d_r = -16; %diversion quantity at this elevation range (1000 ac-ft/yr)
volume_mono = volume_mono + q + v_p + v_e + d_r; %recalculates lake volume (1000 ac-ft)

else if 6377 <= elev_mono < 6380 %calculation only for given elevation range
d_r = -4.5; %diversion quantity at this elevation range (1000 ac-ft/yr)
volume_mono = volume_mono + q + v_p + v_e + d_r; %recalculates lake volume (1000 ac-ft)

else %calculation for all other elevations
d_r = 0; %diversion quantity at this elevation range (1000 ac-ft/yr)
volume_mono = volume_mono + q + v_p + v_e+ + d_r; %recalculates lake volume (1000 ac-ft)

end
end

%record making

volume_record = [volume_record;i volume_mono]; %fills in record for volume
area_record = [area_record;i area_mono]; %fills in record for area
elev_record = [elev_record;i elev_mono]; %fills in record for elevation
q_record = [q_record;i q]; %fills in record for overland flows
p_record = [p_record;i v_p]; %fills in record for precipitation
e_record = [e_record;i v_e]; %fills in record for evaporation
d_record = [d_record;i d_r]; %fills in record for diversions
e_t_record = [e_t_record;i e_t]; %fills in record for target elevation level

end

%create figure

figure(1) %calls figure 1
title('Elevation and Flux of Lake Mono, Ca, 1994-2094') %titles figure 1

subplot(2,1,1) %creates subplot 1 of 2
title('Elevation of Lake Mono') %titles subplot
plot(elev_record(:,1),elev_record(:,2),'-g') %plots elevation vs. time
hold on %holds subplot for additional graph(s)
plot(e_t_record(:,1),e_t_record(:,2),'-b') %plots target elevation vs. time
axis([0,50,6370,6395]) %sets axis limits
xlabel('Years after 1994') %labels x-axis
ylabel('Elevation (ft)') %labels y-axis
legend('Calculated Elevation','Target Elevation','Location','NorthEastOutside') %adds legend to subplot
hold on %holds subplot for additional graph(s)

subplot(2,1,2) %creates subplot 2 of 2
title('Flux') %titles subplot
plot(q_record(:,1),q_record(:,2),'-g',p_record(:,1),p_record(:,2),'-k',e_record(:,1),e_record(:,2),'-b',d_record(:,1),d_record(:,2),'-r')
%prev line: plots overland flows, precipitation, evaporation, and
%diversions vs. time
axis([0,50,-300,300]) %sets axis limits
xlabel('Years After 1994') %labels x-axis
ylabel('Flux (1000 ac - ft)') %labels y-axis
legend('Overland Inflows','Precipitation','Evaporation','Diversions ','Location','NorthEastOutside') %adds legend to subplot
hold on %holds subplot for additional graph(s)

end

And the large loop is actually set on ten timesteps...not twenty.