Getting structure content using strings

I have kt containing data type "strings", one of them is "grad"i.e kt(1,1)=grad which is a string. I am also trying to get the content of the structure(Data.edata.grad) in my data using the string data set by doing Data.edata.kt(1,1) but i am getting the error kt(1,1) is not an existing field. How can i convert a string to a structure or how can i use my string data set to get the structures?

[James Tursa]

Show us the actual code, not your description of it. And copy & paste the entire error message for us to see.

[samuel okeleye]

clear;
clc;

load('Unit 1001 Session 0068.mat')

k=Data.ECU_Data;
m=Data.Continuous_Data;
%CREATING THE FIELDS THAT NEED TO BE CHECKED

fieldcheck={'spn00084_src00_wheel_based_vehicle_speed';...
'spn00190_src00_engine_speed';...
'spn00102_src00_engine_intake_manifold_1_pressure';...
'spn00105_src00_engine_intake_manifold_1_temperature';...
'spn00108_src00_barometric_pressure';... 
'spn00513_src00_actual_engine___percent_torque';...
'spn00110_src00_engine_coolant_temperature';...
'spn00183_src00_engine_fuel_rate';...
'spn00514_src00_nominal_friction___percent_torque';...
'spn00528_src00_engine_speed_at_point_2_engine_configuration';...
'spn00529_src00_engine_speed_at_point_3_engine_configuration';...
'spn00530_src00_engine_speed_at_point_4_engine_configuration';...
'spn00531_src00_engine_speed_at_point_5_engine_configuration';...
'spn00540_src00_engine_percent_torque_at_point_2_engine_configur';...
'spn00541_src00_engine_percent_torque_at_point_3_engine_configur';...
'spn00542_src00_engine_percent_torque_at_point_4_engine_configur';...
'spn00543_src00_engine_percent_torque_at_point_5_engine_configur';...
'spn00544_src00_engine_reference_torque_engine_configuration';...
'spn04154_src00_actual_engine___percent_torque_high_resolution';...
'spn03700_src00_diesel_particulate_filter_active_regeneration_st'};
fieldcheck2={'ambient.temperature';...
'vehicle.speed.gps';...
'vehicle.position.latitude';...
'vehicle.position.longitude';... 
'vehicle.position.altitude'};

%%Channel Existence Check
af1=isfield(k,{'spn00084_src00_wheel_based_vehicle_speed';...
'spn00190_src00_engine_speed';...
'spn00102_src00_engine_intake_manifold_1_pressure';...
'spn00105_src00_engine_intake_manifold_1_temperature';...
'spn00108_src00_barometric_pressure';... 
'spn00513_src00_actual_engine___percent_torque';...
'spn00110_src00_engine_coolant_temperature';...
'spn00183_src00_engine_fuel_rate';...
'spn00514_src00_nominal_friction___percent_torque';...
'spn00528_src00_engine_speed_at_point_2_engine_configuration';...
'spn00529_src00_engine_speed_at_point_3_engine_configuration';...
'spn00530_src00_engine_speed_at_point_4_engine_configuration';...
'spn00531_src00_engine_speed_at_point_5_engine_configuration';...
'spn00540_src00_engine_percent_torque_at_point_2_engine_configur';...
'spn00541_src00_engine_percent_torque_at_point_3_engine_configur';...
'spn00542_src00_engine_percent_torque_at_point_4_engine_configur';...
'spn00543_src00_engine_percent_torque_at_point_5_engine_configur';...
'spn00544_src00_engine_reference_torque_engine_configuration';...
'spn04154_src00_actual_engine___percent_torque_high_resolution';...
'spn03700_src00_diesel_particulate_filter_active_regeneration_st'});

af2=isfield(m,{'ambient.temperature';...
'vehicle.speed.gps';...
'vehicle.position.latitude';...
'vehicle.position.longitude';... 
'vehicle.position.altitude'});

%Available and Unavailable Channels
af1av=fieldcheck(af1==1);
af1unav=fieldcheck(af1==0);

%
af2av=fieldcheck2(af2==1);
af2unav=fieldcheck2(af2==0);
avk=k.af1av

Error
Reference to non-existent field 'af1av'.

Error in QA_QC (line 86)
avk=k.af1av;

[samuel okeleye]

I switched the string to cell for simplicity.

Answer 1

[Walter Roberson]

Data.edata.(kt(1,1))

You might perhaps need to use

Data.edata.(kt{1,1})

[samuel okeleye]

This worked for a single entry. However i have 19 rows and 1 column and it did not work for the rest. I have also changed the data type from string to a different data type for simplicity. Thanks for your assistance

[Walter Roberson]

Note that isfield() returns logical directly, so

af1av=fieldcheck(af1==1);
af1unav=fieldcheck(af1==0);

can be written as just

af1av = fieldcheck(af1);
af1unav = fieldcheck(~af1);

Also, you do not need to code those text strings twice: you can

af1 = isfield(k, fieldcheck);

Anyhow, we have as outsider viewers have no reason to expect that af1av will be a scalar cell array containing only one character vector, so k referenced with fields af1av would be expected to referencing multiple fields. You cannot use the .(field) dynamic fieldname syntax to access multiple fields.

You should consider a different approach such as

kcell = struct2cell(k);
af1 = cell2struct( kcell(af1), af1av, 1);   %not sure that 1 is correct here, possibly 2 instead.

[samuel okeleye]

Thanks for your help. Because k contains a lot of structures, out of which i am selecting few,kcell(af1) only selected the first set of structures within k, through the length of af1. I tried the method below and it worked. Please advise if you think my method is complicated. Thanks

for i=1:length(af1av)
af1avchannel(i)=k.(af1av{i,1});
end

[Walter Roberson]

That code relies upon the fields all being the same datatype and all scalars (either numeric scalars or scalar logical or scalar character or scalar cell array.)

[samuel okeleye]

Thank you.