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From: Linda Davis on 13 Jul 2010 15:33
Remedial, I know: I'm "teaching myself MatLab" and I've only had BASIC about a hundred years ago...I've stumbled again. Using David McMahon's book, I'm trying to write a script following his example (and in his style, which I appreciate, he leads you through examples, then sets you up without spoonfeeding you) and I've missed something critical, but cannot figure out my programming gaff. I'm embarrassed to ask for help, but I have to learn this so that I can actually wrestle with real data from satellites soon!

So, I was to write a script so that I use a for loop to create "an array with individual elements repeated by frequency:" Given a set of employees with their ages, (e.g., two employees aged 17, one employee aged 18, etc.), I create an array of absolute frequency data. then I set the bin width to 1; and the next step is what I think is not being read when I call the script: "create an array that represents the ages ranged from 17 to 43 with a binwidth of one year". Next, we "collect the raw data" using a "For Loop to sweep through the data as" [I've shown below starting with raw =[] to end]
in MatLab's command window then, ave=mean(raw) gives me a number less than 1, whereas the average of the ages should be 30.7308.....and if I just ask it to return the values for raw, I get the array for my f_abs, not the array of all the ages.

Would anyone be able to help me see where I have gone wrong? Please.


%define the function; creating a singular array; the outline in text is
%"gapped"
function f_abs=raw
f_abs=[2,1,0,0,3,0,0,1,0,1,0,4,0,0,2,0,1,2,0,0,3,0,1,2,0,0,3];
binwidth=1;
bins=(17:binwidth:43);
raw=[];
for i = 1:length(f_abs)
if f_abs(i)>0
new = bins(i)*ones(1,f_abs(i));
else
new=[];
end
raw=[raw,new];
end

--
Linda
From: Wayne King on 13 Jul 2010 17:31
"Linda Davis" <linda.l.davis.removethis(a)jpl.nasa.gov> wrote in message <i1if1i$823$1(a)fred.mathworks.com>...
> Remedial, I know: I'm "teaching myself MatLab" and I've only had BASIC about a hundred years ago...I've stumbled again. Using David McMahon's book, I'm trying to write a script following his example (and in his style, which I appreciate, he leads you through examples, then sets you up without spoonfeeding you) and I've missed something critical, but cannot figure out my programming gaff. I'm embarrassed to ask for help, but I have to learn this so that I can actually wrestle with real data from satellites soon!
>
> So, I was to write a script so that I use a for loop to create "an array with individual elements repeated by frequency:" Given a set of employees with their ages, (e.g., two employees aged 17, one employee aged 18, etc.), I create an array of absolute frequency data. then I set the bin width to 1; and the next step is what I think is not being read when I call the script: "create an array that represents the ages ranged from 17 to 43 with a binwidth of one year". Next, we "collect the raw data" using a "For Loop to sweep through the data as" [I've shown below starting with raw =[] to end]
> in MatLab's command window then, ave=mean(raw) gives me a number less than 1, whereas the average of the ages should be 30.7308.....and if I just ask it to return the values for raw, I get the array for my f_abs, not the array of all the ages.
>
> Would anyone be able to help me see where I have gone wrong? Please.
>
>
> %define the function; creating a singular array; the outline in text is
> %"gapped"
> function f_abs=raw
> f_abs=[2,1,0,0,3,0,0,1,0,1,0,4,0,0,2,0,1,2,0,0,3,0,1,2,0,0,3];
> binwidth=1;
> bins=(17:binwidth:43);
> raw=[];
> for i = 1:length(f_abs)
> if f_abs(i)>0
> new = bins(i)*ones(1,f_abs(i));
> else
> new=[];
> end
> raw=[raw,new];
> end
>
> --
> Linda

Hi Linda, Welcome to MATLAB!! The problem is in the way you defined your function. Try this:

Define a function called employdata. Go file -> new script, then copy and paste the following into the empty script.

function Data = employdata(f_abs)
binwidth=1;
bins=(17:binwidth:43);
Data =[];
for i = 1:length(f_abs)
if f_abs(i)>0
new = bins(i)*ones(1,f_abs(i));
else
new=[];
end
Data =[Data,new];
end

Save the file as employdata.m in a directory that is in the MATLAB path. Not sure what platform you are using, but I'll assume Windows for a moment. Create a directory called c:\matlabprogs and save employdata.m in there. Then add that directory to MATLAB's path by entering:

addpath 'c:\matlabprogs'

at the command prompt. Then execute the following (you can just copy and paste):

f_abs=[2,1,0,0,3,0,0,1,0,1,0,4,0,0,2,0,1,2,0,0,3,0,1,2,0,0,3];
Data = employdata(f_abs);

Now you have a variable Data consisting of 26 measurements in your MATLAB workspace. You can now see that

mean(Data)

is 30.7308.

Enter:

hist(Data)

to see a histogram of your data.

Hope that helps,
Wayne
From: Linda Davis on 13 Jul 2010 18:14
Thank you Wayne!
I knew the first part was problematic, Linda

"Wayne King" <wmkingty(a)gmail.com> wrote in message <i1ilv7$fpj$1(a)fred.mathworks.com>...
> "Linda Davis" <linda.l.davis.removethis(a)jpl.nasa.gov> wrote in message <i1if1i$823$1(a)fred.mathworks.com>...
> > Remedial, I know: I'm "teaching myself MatLab" and I've only had BASIC about a hundred years ago...I've stumbled again. Using David McMahon's book, I'm trying to write a script following his example (and in his style, which I appreciate, he leads you through examples, then sets you up without spoonfeeding you) and I've missed something critical, but cannot figure out my programming gaff. I'm embarrassed to ask for help, but I have to learn this so that I can actually wrestle with real data from satellites soon!
> >
> > So, I was to write a script so that I use a for loop to create "an array with individual elements repeated by frequency:" Given a set of employees with their ages, (e.g., two employees aged 17, one employee aged 18, etc.), I create an array of absolute frequency data. then I set the bin width to 1; and the next step is what I think is not being read when I call the script: "create an array that represents the ages ranged from 17 to 43 with a binwidth of one year". Next, we "collect the raw data" using a "For Loop to sweep through the data as" [I've shown below starting with raw =[] to end]
> > in MatLab's command window then, ave=mean(raw) gives me a number less than 1, whereas the average of the ages should be 30.7308.....and if I just ask it to return the values for raw, I get the array for my f_abs, not the array of all the ages.
> >
> > Would anyone be able to help me see where I have gone wrong? Please.
> >
> >
> > %define the function; creating a singular array; the outline in text is
> > %"gapped"
> > function f_abs=raw
> > f_abs=[2,1,0,0,3,0,0,1,0,1,0,4,0,0,2,0,1,2,0,0,3,0,1,2,0,0,3];
> > binwidth=1;
> > bins=(17:binwidth:43);
> > raw=[];
> > for i = 1:length(f_abs)
> > if f_abs(i)>0
> > new = bins(i)*ones(1,f_abs(i));
> > else
> > new=[];
> > end
> > raw=[raw,new];
> > end
> >
> > --
> > Linda
>
> Hi Linda, Welcome to MATLAB!! The problem is in the way you defined your function. Try this:
>
> Define a function called employdata. Go file -> new script, then copy and paste the following into the empty script.
>
> function Data = employdata(f_abs)
> binwidth=1;
> bins=(17:binwidth:43);
> Data =[];
> for i = 1:length(f_abs)
> if f_abs(i)>0
> new = bins(i)*ones(1,f_abs(i));
> else
> new=[];
> end
> Data =[Data,new];
> end
>
> Save the file as employdata.m in a directory that is in the MATLAB path. Not sure what platform you are using, but I'll assume Windows for a moment. Create a directory called c:\matlabprogs and save employdata.m in there. Then add that directory to MATLAB's path by entering:
>
> addpath 'c:\matlabprogs'
>
> at the command prompt. Then execute the following (you can just copy and paste):
>
> f_abs=[2,1,0,0,3,0,0,1,0,1,0,4,0,0,2,0,1,2,0,0,3,0,1,2,0,0,3];
> Data = employdata(f_abs);
>
> Now you have a variable Data consisting of 26 measurements in your MATLAB workspace. You can now see that
>
> mean(Data)
>
> is 30.7308.
>
> Enter:
>
> hist(Data)
>
> to see a histogram of your data.
>
> Hope that helps,
> Wayne
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