Getting a specific row out of a table for two specific inputs in matlab

Good day,

I have a variable of type "dataset" containing the following data in tabular form for a specific year

    Year    Month    Day    Temp_max    Temp_min    Temp_avg
    2005     1        1       21        12.6        15.867  
    2005     2        3       22        11.1        15.292  
    2005     7       21       51.1      18.4        36.35
    So On..................................................

The user will give the inputs of month and day and for those specific month and date I will get the value of T_max and T_min any idea how I can do that ? As I have over 350 rows containing such data ? will be highly obliged if you can help me with the coding of this.

I can access the data of individual columns from Year.Month & Year.Day commands

Answer 1

[Walter Roberson]

right_tablerow = YourTable(:,2) == UserEnteredMonth & YourTable(:,3) == UserEnteredDay;
TableEntry = YourTable(right_tablerow,:);

now you can extract the desired values out of TableEntry

[Hawkins]

Taking my table as variable v (as it contains the whole table part of which is specified above) , I have used D & M for UserEnteredMonth & UserEnteredDay respectively, I have entered a row number for right_tablerow but it is giving me an error, p.s my data has over 366 rows. I don`t think that I can numerically name each one, can you please specify a little further, much obliged for your help, thankyou.

right_tablerow = v(:,2) == M & v(:,3) == D;
TableEntry = v(right_tablerow,:);

[Walter Roberson]

right_tablerow will be a logical index that is true in the locations where both the month and the day matches. Do not enter a particular numeric value for it, let it be calculated. The two lines there appear to be appropriate. You would then follow with something like

Tmin = TableEntry(:,5);
Tmax = TableEntry(:,4);

[Hawkins]

Upon writing this code

right_tablerow = v(:,2) == M & v(:,3) == D;
TableEntry = v(right_tablerow,:);

I recieve this error "Undefined function 'eq' for input arguments of type 'dataset'"

[Hawkins]

The numeric 2 & 3 represent column numbers here?

Theright_tablerow = v(:,2) == M & v(:,3) == D;

[Hawkins]

Walter Roberson can you please help with the code.

[Walter Roberson]

http://www.mathworks.com/help/stats/index-and-search-dataset-arrays.html#bt4qn1r

TableEntries = v(v.Month == M & v.Day == D);
TableEntries.Temp_min
TableEntries.Temp_max

Note: if you have R2013b or later you should switch from dataset to table

[Hawkins]

I did I am getting this error, p.s I am having 2013 how can I switch? I tried converting my data to table format via this, didn`t work :(

    Month = Year.Month
    Day = Year.Day
    MaxT = Year.Temp_max
    MinT = Year.Temp_min
    T = table (Month, Day, MaxT, MinT)

[Hawkins]

Ok I got it how to make the table.

[Walter Roberson]

TableEntries = v(v.Month == M & v.Day == D, :);

If you have R2013a then you would need to upgrade to use tables. If you are using R2013b or later then you might be able to replace your data input with a call to readtable()

[Hawkins]

I am using R2013a :( I tried converting my data to table format via this, didn`t work :(

Month = Year.Month
    Day = Year.Day
    MaxT = Year.Temp_max
    MinT = Year.Temp_min
    T = table (Month, Day, MaxT, MinT)

[Hawkins]

P.s I am so greatful for your help and also for your valuable advice, thanks for working with me, irrespective whether my problem gets solved or not, you were indeed a big help. Thanks

[Hawkins]

Any idea how I can do it with datasets? As I can`t use the tables unfortunately

[Walter Roberson]

uitable is not at all the same, and "table" was not introduced until R2013b so do not worry about using table(). What are you encountering with the code I posted,

TableEntries = v(v.Month == M & v.Day == D);
TableEntries.Temp_min
TableEntries.Temp_max

[Hawkins]

I am encountering the following error it takes me to the subsets of the dataset function, I am thinking of converting the dataset into an excel spread sheet, would it be of any help with regards to the codes? Eagerly waiting for your reply :)

Error using dataset/subsrefParens (line 9)
Dataset array subscripts must be two-dimensional.

Error in dataset/subsref (line 69)
[varargout{1:nargout}] = subsrefParens(a,s);

Error in Untitled4 (line 3)
TableEntries = v(v.Month == M & v.Day == D);

[Walter Roberson]

Please do not open duplicate questions. Your existing question is active and is still on the first page of results. Anyone who would be likely to see your duplicate question would be likely to see your original question.

Remember that I am helping a number of people at the same time, so I cannot always reply promptly to any one question.

[Walter Roberson]

Sorry I forgot that I had posted a correction,

    TableEntries = v(v.Month == M & v.Day == D,:);

[Hawkins]

Thankyou so much, the issue has been resolved. Highly Obliged for your help and time.