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head

Get top rows of table, timetable, or tall array

Syntax

B = head(A)
B = head(A,k)

Description

example

B = head(A) returns the first eight rows of table or timetable A.

example

B = head(A,k) returns the first k rows of A.

Examples

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Create a table that contains 100 rows and five variables.

load patients
T = table(LastName,Gender,Age,Height,Weight);
size(T)
ans = 

   100     5

Preview the first eight rows.

T2 = head(T)
T2=8x5 table
     LastName      Gender     Age    Height    Weight
    __________    ________    ___    ______    ______

    'Smith'       'Male'      38     71        176   
    'Johnson'     'Male'      43     69        163   
    'Williams'    'Female'    38     64        131   
    'Jones'       'Female'    40     67        133   
    'Brown'       'Female'    49     64        119   
    'Davis'       'Female'    46     68        142   
    'Miller'      'Female'    33     64        142   
    'Wilson'      'Male'      40     68        180   

Create a tall table and preview the first few rows of data.

Create a tall table for the airlinesmall.csv data set. Select a subset of the variables to work with. Use head to extract the first few rows of data.

varnames = {'Year','Month','ArrDelay','DepDelay','UniqueCarrier'};
ds = datastore('airlinesmall.csv','TreatAsMissing','NA',...
    'SelectedVariableNames',varnames);
T = tall(ds)
T =

  Mx5 tall table

    Year    Month    ArrDelay    DepDelay    UniqueCarrier
    ____    _____    ________    ________    _____________

    1987    10        8          12          'PS'         
    1987    10        8           1          'PS'         
    1987    10       21          20          'PS'         
    1987    10       13          12          'PS'         
    1987    10        4          -1          'PS'         
    1987    10       59          63          'PS'         
    1987    10        3          -2          'PS'         
    1987    10       11          -1          'PS'         
    :       :        :           :           :
    :       :        :           :           :
tt = head(T)
tt =

  8x5 tall table

    Year    Month    ArrDelay    DepDelay    UniqueCarrier
    ____    _____    ________    ________    _____________

    1987    10        8          12          'PS'         
    1987    10        8           1          'PS'         
    1987    10       21          20          'PS'         
    1987    10       13          12          'PS'         
    1987    10        4          -1          'PS'         
    1987    10       59          63          'PS'         
    1987    10        3          -2          'PS'         
    1987    10       11          -1          'PS'         

Collect the results into memory to view the data.

t8 = gather(tt)
Evaluating tall expression using the Local MATLAB Session:
Evaluation completed in 0 sec
t8=8x5 table null
    Year    Month    ArrDelay    DepDelay    UniqueCarrier
    ____    _____    ________    ________    _____________

    1987    10        8          12          'PS'         
    1987    10        8           1          'PS'         
    1987    10       21          20          'PS'         
    1987    10       13          12          'PS'         
    1987    10        4          -1          'PS'         
    1987    10       59          63          'PS'         
    1987    10        3          -2          'PS'         
    1987    10       11          -1          'PS'         

Preview the first 20 rows of data in a tall table.

Create a tall table for the airlinesmall.csv data set. Select a subset of the variables to work with, and treat 'NA' values as missing data so that datastore replaces them with NaN values. Use head to view the first 20 rows of data.

varnames = {'Year','Month','ArrDelay','DepDelay','UniqueCarrier'};
ds = datastore('airlinesmall.csv','TreatAsMissing','NA',...
    'SelectedVariableNames',varnames);
T = tall(ds)
T =

  Mx5 tall table

    Year    Month    ArrDelay    DepDelay    UniqueCarrier
    ____    _____    ________    ________    _____________

    1987    10        8          12          'PS'         
    1987    10        8           1          'PS'         
    1987    10       21          20          'PS'         
    1987    10       13          12          'PS'         
    1987    10        4          -1          'PS'         
    1987    10       59          63          'PS'         
    1987    10        3          -2          'PS'         
    1987    10       11          -1          'PS'         
    :       :        :           :           :
    :       :        :           :           :
tt = head(T,20)
tt =

  20x5 tall table

    Year    Month    ArrDelay    DepDelay    UniqueCarrier
    ____    _____    ________    ________    _____________

    1987    10        8          12          'PS'         
    1987    10        8           1          'PS'         
    1987    10       21          20          'PS'         
    1987    10       13          12          'PS'         
    1987    10        4          -1          'PS'         
    1987    10       59          63          'PS'         
    1987    10        3          -2          'PS'         
    1987    10       11          -1          'PS'         
    :       :        :           :           :
    :       :        :           :           :

Collect the results into memory to view the data.

t20 = gather(tt)
Evaluating tall expression using the Local MATLAB Session:
Evaluation completed in 0 sec
t20=20x5 table
    Year    Month    ArrDelay    DepDelay    UniqueCarrier
    ____    _____    ________    ________    _____________

    1987    10         8         12          'PS'         
    1987    10         8          1          'PS'         
    1987    10        21         20          'PS'         
    1987    10        13         12          'PS'         
    1987    10         4         -1          'PS'         
    1987    10        59         63          'PS'         
    1987    10         3         -2          'PS'         
    1987    10        11         -1          'PS'         
    1987    10         3          3          'PS'         
    1987    10         2          1          'PS'         
    1987    10        16         15          'PS'         
    1987    10         3          9          'PS'         
    1987    10        39         15          'PS'         
    1987    10        57         32          'TW'         
    1987    10         0         -3          'TW'         
    1987    10       -14          0          'TW'         

Input Arguments

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Input array, specified as a table or timetable.

Data Types: table | timetable

Number of rows to extract, specified as a positive scalar integer. If A has fewer than k rows, then head returns all of A.

Output Arguments

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Requested rows, returned as a table or timetable. The data type of B is the same as A.

Extended Capabilities

Introduced in R2016b

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