problem using hold on in a for loop

For my project, I am calculating the half-life of an organism based on radioactive decay. My code is below. The problem I am experiencing is that he figure only has one point plotted. If someone could explain how to fix this so my entire function would be plotted, that would be greatly appreciated.

function Project
clc, clear
P=menu ('Please choose the element', 'Pm-145', 'Po-209', 'Ra-226', 'Ac-227', 'Am-243', 'Bk-247', 'Cf-251', 'C-14');
switch P %P=element found in sample through AMS
    case 1          % Promethium-145
        t=17.4;
    case 2          % Polonium-209
        t=102;
    case 3          % Radium-226
        t=1600;
    case 4          % Actinium-227
        t=21.77;
    case 5          % Americium-243
        t=7370;
    case 6          % Berkelium-247
        t=1380;
    case 7          % Californium-251
        t=898;
    case 8          % Carbon-14
        t=5730;
end
N=input ('Please enter the remaining percentage of substance: \n');
while N<=0 || N>=100 %N=percentage of element found through AMS 
    fprintf ('Incorrect input. Please try again. \n');
    N=input ('Please enter the remaining percentage of substance: \n');
end
clc
age=(((log((N)/(100)))/(-0.693))*t);
fprintf ('The age of your organism is shown below: \n');
fprintf (' %s years',age);

n=length(N);
for i=1:n
    plot(age(i), N(i), '*', 'MarkerSiz', 10)
    xlim([0 inf])
    ylim([0 100])
    pause(.01)
    hold all
    xlabel(strcat('Years passed = ', num2str(age(i))))  
    ylabel(strcat('Percentage remaining =', num2str(N(i)))) 
    title ('Radioactice Decay')
    grid on
end
end

Thanks!

[the cyclist]

FYI, I used the CODE button to format your code. See how much easier it is to read now?!

[Bobby Huxford]

Not certain what function it is you mean.

age and N are scalar values, so the plot should only produce one point? It also looks like the for loop only executes once, so it is not necessary.

[Rebekah Kuehl]

I am wanting the formula "age" to be plotted on the figure (the exponential decay for a half-life)

How would I fix my code to enable this? Do I need to change age and N?

[Adam]

What are you trying to do in this while loop?

while N<=0 || N>=100 %N=percentage of element found through AMS 
    fprintf ('Incorrect input. Please try again. \n');
    N=input ('Please enter the remaining percentage of substance: \n');
end

Currently it just keeps asking the user to input things and then throws them away by overwriting them next time round. Is it your intention to keep all the N values entered?

In which case you need to concatenate them into an array.

[Rebekah Kuehl]

The input requested is a percentage, so the while loop is used to get an appropriate number. For example, if the user inputs a negative number or one larger than 100, the program will not run because those are not acceptable percentages

[Adam]

Ah, ok. So N is scalar, as others have mentioned, for all subsequent analysis.

Answer 1

[the cyclist]

Your variable N is a single value -- a scalar. (It is an array of length 1.) You then define n to be the length of that array. So n = 1.

Then, you plot in a for loop that goes from 1 to n. But that's from 1 to 1. So, you get one point.

[Rebekah Kuehl]

Thanks, I think I understand why it only plotted the one point. How would I go about fixing it to plot the line for the function "age"?

[David K.]

After you get the input for N, you could make it a vector with code like

N = 1:N;

Then if you want it to plot starting at the given percentage you could do

N = fliplr(N);

[Rebekah Kuehl]

Where would I place the vector code that you posted?

[David K.]

Right before you calculate age.