How do I change a string object into a variable name that heatmap accepts

I have a string array of table variable names that i want to feed into heatmap. I use 'for' to loop through a table to generate heatmaps that go to power point.

heatmap(engine_config, group_perms(i,1), group_perms(i,2))

I get this error.

Error using heatmap
'XVariable' value does not refer to a valid variable in the source table.

Caused by:
    Unrecognized table variable name 'group1'.

heatmap wants this, not string:

heatmap(engine_config, 'group_1', 'group_2')

This is probably a real simple solution. I have not nailed down the use of brackets/parenthases to get the right data type.

I have tried some matlab conversions but no luck.

Any help is appreciated.

group_perms 10x2 string

group1	group2
group1	group4
group1	group5
group1	group3
group2	group4
group2	group5
group2	group3
group4	group5
group4	group3
group5	group3

obtained using

group_perms = nchoosek(group_vars, 2);

group_vars is a string array of a subset of variable names in my large dataset. I use my string array throughout my program.

Answer 1

[Adam Danz]

If nchoosek returns a cell array of strings, you can index them using { }

try this.

heatmap(engine_config, group_perms{i,1}, group_perms{i,2})

or this to convert it to string array

group_perms = string(nchoosek(group_vars, 2));
heatmap(engine_config, group_perms(i,1), group_perms(i,2))

[Ted H]

Same error for both attempts.

I also tried changing the string array to a cell array, also with same error.

[Adam Danz]

For my own sanity, could you show me exactly what this returns:

group_perms(i,1)

As well as this

engine_config.Properties.VariableNames

assuming this is your table.

[Ted H]

Thanks. This found my problem. There was a variable name in the string array that ended up not being in my table (its a large table with changes). And I read the error message as being a data type issue, not a missing object issue.

heatmap(engine_config, group_perms(i,1), group_perms(i,2))

is the correct syntax.

Thanks!

Answer 2

[Steven Lord]

This seems to work with a simpler example.

T = array2table(magic(5))

T = 5×5 table
    Var1    Var2    Var3    Var4    Var5
    ____    ____    ____    ____    ____

     17      24       1       8      15 
     23       5       7      14      16 
      4       6      13      20      22 
     10      12      19      21       3 
     11      18      25       2       9 

V = string(T.Properties.VariableNames)

V = 1×5 string array
    "Var1"    "Var2"    "Var3"    "Var4"    "Var5"

heatmap(T, V(2), V(5)) % Using variables 2 and 5 as an example

Looking at your code, the example you posted that you said worked used "group_1" and "group_2" as variable names but the error message calls out that "group1" (no underscore) is not a variable in your table. What do your group_perms and group_vars variables contain: "group_1" or "group1"?

[Ted H]

See comment in other answer. I did find the problem and it is a missing object (wrong variable name), not a data type problem, which I assumed when i read the error.