I had the same problem.
Things that don't work
Matlab itself refuses to load data from a .mat file if the variable name involved is invalid.
There are multiple ways to call the load() function
load("myfile.mat")
load("myfile.mat","variable name with spaces")
%obviously fails since the variable names in the file are invalid
%and can't be created in the workspace.
struct=load("myfile.mat")
%structs can't contain invalid variable names either
valid_varname=load("myfile.mat","variable name with spaces")
%this fails too, Matlab validates the name before retrieving it
%from the file
None of them work of course. Even if there's nothing technically stopping the last command from working Matlab still refuses to touch invalid variable names.
I tried using the LOADFIXNAMES library but that did not work for me. After installing the compiler (MinGW-w64) the extension compiled but crashed matlab as soon as I called it with my files.
What did work
Anaconda (A python programming language bundle) includes the scipy library. The scipy.io library has the loadmat() and savemat() functions which read and write matlab data files. Loadmat produces a data structure containing the (name,value) pairs for all variables in the file. The names can be changed and the new (name,value) pairs put into a similar structure and fed to savemat to produce a fixed output file.
Here's the code I used: (Note that this is python code not matlab code)
import scipy.io as sio
import pathlib
import string
def fix_name(name):
name="".join(c for c in name if c in string.ascii_letters+string.digits+"_")
if name[0] not in string.ascii_letters:#name must start with a letter
name="X"+name
name=name[:63]#names may not be longer than 63 chars
return name
ignore_names=["__header__","__version__","__globals__"]
def fix_struct(s):
out_struct=dict()
for name,value in s.items():
if name not in ignore_names:
out_struct[fix_name(name)]=value
return out_struct
def struct_needs_fixing(s):
for name in s.keys():
if name not in ignore_names:
if fix_name(name)!=name:
return True
return False
root=r"C:\someplace\folder_with_the_files"
root=pathlib.Path(root)
files=list(root.glob("*.mat"))#get all the .mat data files in the directory
Overwrite=False #overwrite files in place
for f in files:
new_f=f.parent/("fixed_"+f.name)#save the modified file with a prefix
if Overwrite:new_f=f
struct=sio.loadmat(str(f))
if struct_needs_fixing(struct):
print("fixing",str(f))
struct=fix_struct(struct)
sio.savemat(new_f,struct)
else:
print("skipping",str(f))
This removes all unallowed chars and prefixes names with "X" if they don't already start with a letter.
Anaconda itself takes about 20 minutes to install. The code above can be run from jupyter notebook which should be available in the start menu after installing anaconda. The file path can be copied from the windows file explorer (right-click on file)-->properties-->(popup window)-->location The above script will fix all the files in a given folder.
