Question

load command matlab

Answer 1

@jim_thompson5910

Answer 2

so i have some data in an excel file. I had imported it into matlab using the tab that says import, however I want to learn how to import the file using the load command.

Answer 3

Let me take a pic of the assignment.

Answer 4

^There is the assignment.

Answer 5

so the 12x31 matrix is located in the workspace. since it's in the workspace does that mean it's already important in matlab?

Answer 6

I think you mean 31x12 ?

Answer 7

it says 12x31

Answer 8

odd, the pdf you posted has 31x12 but your workspace shows 12x31

Answer 9

did you transpose the matrix somewhere?

Answer 10

i just uploaded the file from my instructors spotify. it's a 12x31. He must have made a typo.

Answer 11

no I didn't transpose it anywhere.

Answer 12

on your pdf, it also says "check row 31..." but the workspace has that matrix with only 12 rows

Answer 13

so yeah there has to be a typo in the pdf or a mistake with the xls file

Answer 14

yeah your xls file is 12x31, so the pdf must have the typo

Answer 15

Okay. So how do we use the load command?

Answer 16

weatherData = load(weatherdata) put this in my script and run? Since the 12x31 matrix is in the workspace does that mean it's already uploaded?

Answer 17

I'm guessing that `lab02.m` had the matrix built into it? Can I see the source code you have for that?

Answer 18

wait, nvm, it says to make a new file. So you'd have to import the data in. The question is, how did you import it? Did you use another tool? Or was it already done for you?

Answer 19

I used the import tab. I can post a pic if you like a visual.

Answer 20

no that's fine. I know what you're talking about. So what you should do is clear everything out and try out the bit of code `weatherData = load(weatherdata)` to see if it works or not

Answer 21

>> weatherData = load(weatherdata)
Error using load
Argument must contain a string.

>>

Answer 22

ok so I'm reading here

http://www.mathworks.com/help/matlab/import_export/supported-file-formats.html

that the `load` command only works for MAT files (or ASCII text files but that's a different article). To get XLS files to work, you'll need to use the `xlsread` command

http://www.mathworks.com/help/matlab/ref/xlsread.html

Answer 23

so it would look like this

A = xlsread(filename)

replace A with the matrix you want to call it
replace filename with the string of the file's name, make sure to use single quotes

example:

weatherData = xlsread('weatherdata.xls');

the semicolon is used to suppress output to the command window

Answer 24

okay give me a sec

Answer 25

btw you'll have to make sure that the matlab `.m` file and the `.xls` file are in the same directory

Answer 26

yep same file. give me a sec

Answer 27

oh I see in the pdf it says "transpose the data" so I can see why it went from 31x12 to 12x31

Answer 28

but the excel file in the directory given to us is a 12x31. Maybe transpose later?

Answer 29

wait a minute, before you set up lab02.m, did you make a file called weather_data.MAT ?

Answer 30

no

Answer 31

I'm looking at the prelab part

Answer 32

i downloaded the excel then i imported it into matlab. the excel file is called weather_data and the 12x31 matrix in the workspace is called weatherdaya

Answer 33

did you do this part `save(’weather_data’, ’weatherData’)`

Answer 34

no I didn't. BTW we put this in the script or command window?

Answer 35

it sounds like it's done in the command window

Answer 36

>> save('weather_data','weatherData')
Error using save
Variable 'weatherData' not found.

Answer 37

so if I'm reading the prelab instructions right, I think you're supposed to

step 1) import the xls file into matlab's workspace
step 2) save the data to a file (like a MAT file) that can be used by the `load` command later

Answer 38

you cleared things out. You'll have to re-import

Answer 39

i did clear everything out. let me re-import

Answer 40

okay i have a file named MATLAB and it has lab02.m and weather_data.xls saved there

Answer 41

I imported the data and it is shown in the worksapce window as a 12x31 matrix

Answer 42

ok now do `save(’weather_data’, ’weatherData’)`

Answer 43

kk

Answer 44

>> var1 = save('weather_data','weatherData')
Error using save
Too many output arguments.

Answer 45

hmm strange

Answer 46

weatherData is the name of the variable in your workspace right?

Answer 47

no small d it is weatherdata

Answer 48

weather_data = xls

Answer 49

>> save('weatherData','weatherdata')

Answer 50

so when I apply this command it doesn't give me an error.

Answer 51

ok so it sounds like it was just an issue with upper/lower case letters

Answer 52

does does that mean it works?

Answer 53

so the save command re-defined the matrix in terms of a variable in this case "weatherData"

Answer 54

when I type in "weatherdata" in the command window it outputs the matrix

Answer 55

weatherData just gives me an error

Answer 56

>> weatherData
Undefined function or variable 'weatherData'.

Did you mean:
>> weatherdata

weatherdata =

Columns 1 through 13

0 0 272 0 0 0 0 9 26 1 0 0 0
61 103 0 2 0 0 0 2 0 68 3 3 1
2 0 17 27 0 10 0 0 30 25 0 0 0
260 1 0 0 0 1 3 0 5 0 0 0 0
47 0 0 0 5 115 49 81 0 0 0 0 1
0 0 30 42 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 7 0 0 58 157 52
0 45 0 0 0 0 0 0 5 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 14 156 0 0 0 0 110 130 0 14
1 163 5 0 0 0 0 0 0 0 0 1 0
0 0 0 0 0 45 0 0 0 15 37 0 36

Columns 14 through 26

50 85 0 0 90 9 0 0 1 15 224 0 0
0 0 0 1 135 3 66 0 0 0 5 0 0
45 70 0 0 0 0 0 27 26 0 0 9 6
0 10 51 0 0 0 0 0 0 0 0 0 9
10 1 0 0 0 10 0 0 0 0 0 0 0
0 0 97 133 0 0 0 0 0 2 2 240 16
0 0 0 0 0 7 0 21 0 0 0 10 0
6 0 0 0 0 0 0 1 0 0 158 62 1
0 0 0 0 0 0 0 0 37 0 0 0 0
19 0 0 0 0 0 30 92 0 0 0 0 0
0 0 0 0 0 0 1 26 0 2 2 10 255
97 0 0 0 0 0 20 2 34 0 0 0 0

Columns 27 through 31

0 0 0 33 33
0 62 0 0 0
78 0 5 8 0
35 13 86 0 0
2 0 0 0 0
35 14 14 8 0
0 5 0 0 0
0 0 0 0 0
6 138 58 10 0
0 0 0 0 1
2 0 0 0 0
0 0 0 0 0

Answer 57

strange considering how the pdf has an uppercase D

Answer 58

could be another typo

Answer 59

ok so far in the prelab set up we've imported the xls file into matlab's workspace

then you use the save command to save the data into a MAT file which matlab can read/write to

then when it comes to the lab02.m file, you'll rely on the MAT file to import the data (not the xls file). Remember the `load` command doesn't work with xls files but it works with MAT files

Answer 60

okay so when I download the xls file I need to change the format to an MAT format?

Answer 61

no, the xls file stays intact in the folder

Answer 62

no wait the weatherData.mat is actually saved in the current file

Answer 63

I can see it in under current folder

Answer 64

what are all the files in the folder you're working with?

Answer 65

ok there should be `weather_data.mat` in there too

Answer 66

that is weatherData

Answer 67

hmm odd and you definitely typed ` save(’weather_data’, ’weatherData’)` and not this `save(’weatherData’,’weather_data’)` right?

Answer 68

>> save('weather_data', 'weatherData')
Error using save
Variable 'weatherData' not found.

Answer 69

show me your workspace againplease

Answer 70

something isn't transferring but I'm not sure what

Answer 71

hold on my email is being weird

Answer 72

btw, you can take a screenshot with your computer and you dont' have to use your phone to take pics

Answer 73

you mean print screen. mine doesn't work for some reason.

Answer 74

I think there is a setting on my laptop... I have not looked into it yet.

Answer 75

ok for some reason, it's called `weatherdata` instead of `weatherData`

try

`save('weather_data','weatherdata')`

Answer 76

sweet i have weather_data.mat and weatherData.mat in current folder

Answer 77

ok either delete weatherData.mat or move it to another folder so matlab can't see it anymore

keep weather_data.mat

Answer 78

okay i deleted it

Answer 79

ok so we're done with the prelab stuff

Answer 80

in your lab02.m file, make sure you have the load command set up so you can import the data from the MAT file into the workspace

keep in mind every time you run this m file, it will clear the command line (clc command) and clear the workspace (clear command). So this is why the load command is needed.

Answer 81

S = load(weather_data);

Answer 82

try `load(weather_data)`, without the S in front, and tell me what pops up into your workspace

Answer 83

make sure your workspace is cleared first

Answer 84

>> load(weather_data)
Undefined function or variable 'weather_data'.

Did you mean:
>> load(weatherdata)
Error using load
Argument must contain a string.

Answer 85

oh wait, you need single quotes

Answer 86

try `load('weather_data')`

Answer 87

>> S = load('weather_data')

S =

weatherdata: [12x31 double]

Answer 88

"Argument must contain a string" means you must use single quotes

Answer 89

did you try it without the S in front?

Answer 90

>> load('weather_data')
>>
>>
>>
>>

Answer 91

it doesn't do anything