Question

Use the value in month to extract that month's data from your weatherData matrix and store it
in a new vector m. Because January has 31 days, you should only see values in m that are positive
or zero (no values of -99999 ).

Answer 1

@reemii

Answer 2

Okay so this is only a small part of an assignment.

Answer 3

so i imported the xls file into matlab and used a command to convert it into an MAT file. So I have it saved in my current folder as MAT. The part I posted I don't understand what it is asking.

Answer 4

M = weatherdata

Answer 5

From what I read, I think you must write
\(\verb+month = 1+\)
somewhere and then just extract the data:
\(\verb|januaryData = weatherData[month];|\) (does this work?)

The person making the statement knows the values for January are all >= 0. It's kind of a check for you that you did it right..

Answer 6

hold on

Answer 7

>> JanData = weatherdata(month)

JanData =

0

Answer 8

what is the result of `size(weatherdata)` ?

Answer 9

it's a 12x31 that is a typo btw

Answer 10

i mean 31x12 is a typo

Answer 11

the xls file came in a 12x31 matrix

Answer 12

If weatherdata(month) gives `0`, that means weatherdata is a vector (1 x 365) , isn't it ?

Answer 13

maybe it's your method to load the matrix that isn't right

Answer 14

your first comment I am not sure what you mean 1x365. the zero (0) indicates that somethng is at fault?

Answer 15

the excel file is a 12x31 matrix. The file the instructor provided us

Answer 16

What I think is: if weatherdata is indeed 31x12 (or 12x31), then weatherdata(1) is going to be a vector of length 12 (or 31).

But weatherdata returned `0`, a number. I think that 0 is the first value of what should be the "data vector" for January.

Answer 17

Okay I see what you are saying. Hmmmm

Answer 18

So I asked you to type `size(weatherdata` and see if everything is alright..

Answer 19

>> size(weatherdata)

ans =

12 31

Answer 20

maybe you must write `weatherdata(month,:)` . try this..

Answer 21

>> weatherdata(month,:)

ans =

Columns 1 through 12

0 0 272 0 0 0 0 9 26 1 0 0

Columns 13 through 24

0 50 85 0 0 90 9 0 0 1 15 224

Columns 25 through 31

0 0 0 0 0 33 33

Answer 22

Is it possible? (I don't know enough to say)

Answer 23

hmmm

Answer 24

try weatherdata(12:31) and weatherdata(31:12).. which one is "error" ?

I forgot if matlab stores data in matrices by columns or rows .

Answer 25

weatherdata(31:12)

ans =

Empty matrix: 1-by-0

Answer 26

that is the wrong one.

Answer 27

>> weatherdata(12:31)

ans =

Columns 1 through 12

0 0 103 0 1 0 0 0 45 0 0 163

Columns 13 through 20

0 272 0 17 0 0 30 0

Answer 28

sorry. I meant, weatherdata(12,31) VS weatherdata(31,12)

Answer 29

>> weatherdata(12,31)

ans =

0

>> weatherdata(31,12)
Index exceeds matrix dimensions.

Answer 30

@phi

Answer 31

ok, first index is for months, second one is for days.
Then weatherdata(month, 1:31) (is probably the same as weatherdata(month,:) , but check it) is the correct code.

Answer 32

this is a bit long.

Answer 33

can you summarize what you are trying to do ?

Answer 34

@reemii i thought you left that is why I called phi over.

Answer 35

@reemii those are both the same

Answer 36

ok , I see the pdf write up.
But it's a bit hard to demonstrate without the data.

Answer 37

laptop crash :-)

Answer 38

can you post the data here?

Answer 39

well I have the data important into lab and converted into mat file

Answer 40

I think that the problem is solved. @phi @raffle_snaffle

Answer 41

let me post the data here. give me a sec

Answer 42

@reemii how so?

Answer 43

I made you check that the size of the matrix is 12x31:
`weatherdata(1,:)` gives you a vector of 31 values.

Answer 44

are we in an agreement that the 12x31 matrix is legit and it's not suppose to be 31x12?

Answer 45

@phi that 31x12 is a typo

Answer 46

1) You know how to access to the data. So it's fine.
2) Maybe it's not a typo, I think that MATLAB stores matrices' rows "vertically" .. something like that. Anyway, 1) is more important than 2).

Answer 47

OK, I loaded it into Octave (freeware version of matlab) and have a 12 x 31 matrix

Answer 48

I assume the 12 is the month.

if you want all the data for the nth month
you would do
A= weather_data(n,:)

for example, for Jan (month 1) you would get
>> Jan= weather_data(1,:)
Jan =

Columns 1 through 14:

0 0 272 0 0 0 0 9 26 1 0 0 0 50

Columns 15 through 28:

85 0 0 90 9 0 0 1 15 224 0 0 0 0

Columns 29 through 31:

0 33 33

Answer 49

what did you define n as ? is that your month?

Answer 50

>> A = weatherdata(n,:)
Undefined function or variable 'n'.

Answer 51

Here is part of what they want

>> month= 1
month = 1
>> m= weather_data(month,:)
m =

Columns 1 through 14:

0 0 272 0 0 0 0 9 26 1 0 0 0 50

Columns 15 through 28:

85 0 0 90 9 0 0 1 15 224 0 0 0 0

Columns 29 through 31:

0 33 33

>> m_avg= mean(m)
m_avg = 27.355
>> m_max= max(m)
m_max = 272
>>

Answer 52

Okay that is nice to know I was in the right direction after m = weathedata(month,:)

Answer 53

Okay I think that is all I wanted to know for now. Thanks for clearing that up for me @phi.

Answer 54

wait. how would we % days in which max. rain fell in inches

Answer 55

For the days on which the max occurs, do
d_max= find(m==m_max)

Answer 56

d_zero= find(m==0)
d_zero =

Columns 1 through 17:

1 2 4 5 6 7 11 12 13 16 17 20 21 25 26 27 28

Column 18:

29

Answer 57

>> nd_zero= length(d_zero)
nd_zero = 18

Answer 58

>> d_max = find(m == m_max)
Undefined function or variable 'm_max'.

Answer 59

oops...

Answer 60

you have to find m_max before you can use it. It is (almost) the first thing I did way up above.

Answer 61

clc ; clear % clear window and workspace
month = 1; % defined variable
m = weatherdata(month,:); % extract months data

m_avg = mean(m); % average rain fall per day in inches
m_max = max(m); % max. rain fall per day in inches
d_max = find(m == m_max); % days in which max. rain fell in inches

Answer 62

yes, that should work.

>> d_nonzero= find(m>0)
d_nonzero =

3 8 9 10 14 15 18 19 22 23 24 30 31

Answer 63

Error in lab02 (line 7)
m = weatherdata(month,:); % extract months data

Answer 64

what is the name of your data? I thought it was weather_data

Answer 65

>> nd_nonzero= length(d_nonzero)
nd_nonzero = 13

Answer 66

>> m_avg_nonzero= mean(m(d_nonzero))
m_avg_nonzero = 65.231

Answer 67

it's but for the longest time i was useing weatherdata and it was ouputting the vector

Answer 68

if you type
whos
it shows what variables exist

Answer 69

now my data doesn't want to load,, let e try that @phi

Answer 70

i cleared everything from my workspace and tried to load(weather_data)

Answer 71

okay I need to restart matlab... It's not running any of the code in my command window

Answer 72

I would use quotes around the filename
load("weather_data")

Answer 73

lol @phi thanks.

Answer 74

clc ; clear % clear window and workspace
month = 1; % defined variable
m = weatherdata(month,:); % extract months data

m_avg = mean(m); % average rain fall per day in inches
m_max = max(m); % max. rain fall per day in inches
d_max = find(m == m_max); % days in which max. rain fell in inches

Answer 75

so when I load(weather_data) into my workspace it appears in the workspace as weatherdata without the _

Answer 76

Reference to a cleared variable weatherdata.

Error in lab02 (line 8)
m = weatherdata(month,:); % extract months data

Answer 77

yes, if you save variables to a file, you can name the file anything you want.
you could for example, save("my_stuff") and it saves the entire workspace

Answer 78

what do you get after loading the file?
can you post the result of
whos
?

Answer 79

>> whos
Name Size Bytes Class Attributes

month 1x1 8 double

>>

Answer 80

no weather data?

try to load it and do whos again

Answer 81

>> whos weatherdata
Name Size Bytes Class Attributes

weatherdata 12x31 2976 double

Answer 82

do you do a clear *after* the load? that is a bad idea
you want to do the clear
then load the data

Answer 83

>> clear
>> load('weather_data')
>> whos weatherdata
Name Size Bytes Class Attributes

weatherdata 12x31 2976 double

Answer 84

clc ; clear % clear window and workspace
load('weather_data')
month = 1; % defined variable
m = weatherdata(month,:); % extract months data

m_avg = mean(m); % average rain fall per day in inches
m_max = max(m); % max. rain fall per day in inches
d_max = find(m == m_max); % days in which max. rain fell in inches

Answer 85

okay got it

Answer 86

okay it runs well so far. I am going to finish putting in the rest of the commands.

Answer 87

clc ; clear % clears command and workspace window
load('weather_data'); % loads data
month = 1; % defined variable
m = weatherdata(month,:); % extract months data

m_avg = mean(m) % average rain fall per day in inches
m_max = max(m) % max. rain fall per day in inches
d_max = find(m == m_max) % days in which max. rain fell in inches
d_zero = find(m == 0) % days in which zero inches fell per day
nd_zero = length(d_zero) % number of days in which zero inches fell per day
d_nonzero = find(m>0) % days in which at least some rain fell

Answer 88

I had to fix a few things

Answer 89

hold up for a sec. I need to read up on the command find and command length

Answer 90

>> A = [1 4 12 0 9 2];
>> find(A)

ans =

1 2 3 5 6

Answer 91

in our case we were telling find what to do? find(m == m_max);

find the month with the max rainfall?

Answer 92

find(A) would return the indices of where A is non-zero

find(m== m_max)
returns the indices where the value == the max value
for example, try it on

tmp= [1 5 5 1]
find(tmp==5)
will return 2 and 3 because tmp(2) and tmp(3)= 5